Imaging system and endoscope

Abstract

The present application relates to an imaging system and an endoscope, comprising a first lens, a second cemented lens group, a second lens, a first cemented lens group and a light transmission element, which are arranged in sequence from the object side to the image side, wherein the first lens has negative optical power, the object side surface of the first lens is a plane, and the image side surface is a concave surface, the second lens has positive optical power, the object side surface and the image side surface of the second lens are both convex surfaces, the object side surface and the image side surface of the second cemented lens group are both planes, the first cemented lens group includes a third lens and a fourth lens, wherein the third lens has positive optical power, the object side surface and the image side surface of the third lens are both convex surfaces, the fourth lens has negative optical power, the object side surface of the fourth lens is concave surface, and the image side surface is convex surface, the image side surface of the third lens is cemented to the object side surface of the fourth lens, the object side surface and the image side surface of the light transmission element are both planes, and the imaging system also satisfies and.

Description

Technical Field

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

[0002] With the continuous advancement of modern medical technology, the demand for minimally invasive surgery is becoming increasingly diverse and complex. Traditional optical microscopes, due to their inherent limitations, are no longer able to meet the growing demand for surgery. This has led to the emergence of electronic microscopes, offering superior performance parameters comparable to those of optical microscopes. Miniaturized electronic lenses, with their high resolution, low distortion, and excellent optical performance, successfully offset the inherent shortcomings of optical microscopes, enabling them to adapt to a wider range of surgical scenarios, such as the nasal cavity, laryngeal cavity, gastric cavity, and urinary system. Furthermore, electronic microscopes feature extremely low light energy loss, enabling 100% light energy transmission, a feat unmatched by optical microscopes. Therefore, electronic microscopes are becoming an indispensable and important tool in minimally invasive surgery within the medical device field.

[0003] An existing electronic endoscope is shown in the electronic endoscope imaging lens of CN112006639B. In this patent, two biconcave lenses are set at the front end of the lens to expand the field of view of the electronic endoscope. Specifically, it can form images within a range of 140°, but the depth of field effect is poor; another endoscope lens is shown in an endoscope imaging lens of CN107544127B. In this patent, the focal length of the lens, the radius of curvature of the lens and the total length of the optical system in the lens group are restricted so that a short-length, small-diameter imaging lens can also have a high imaging quality, which is beneficial to improving the success rate of intracavitary surgery. However, some of the lenses in the lens group are special-shaped lenses, that is, they are not ordinary meniscus lenses, and the object side and image side of the special-shaped lenses have aspherical designs, which makes the lens processing more difficult and the production cost higher. Summary of the Invention

[0004] Since the existing electronic endoscope lens has the disadvantages of unsatisfactory depth of field effect and great difficulty in lens processing, it is necessary to provide an imaging system and an endoscope.

[0005] According to one aspect of the present application, the present application provides an imaging system, comprising:

[0006] A first lens having negative optical power, wherein the object-side surface of the first lens is flat and the image-side surface is concave;

[0007] a second cemented lens group, wherein the object-side surface of the second cemented lens group is a plane and the image-side surface is a plane;

[0008] a second lens having positive optical power, wherein the object-side surface and the image-side surface of the second lens are convex;

[0009] a first cemented lens group, comprising a third lens and a fourth lens, wherein the third lens has positive power, the object-side surface of the third lens is convex, and the image-side surface of the third lens is convex; the fourth lens has negative power, the object-side surface of the fourth lens is concave, and the image-side surface of the fourth lens is convex; and the object-side surface of the fourth lens is cemented to the image-side surface of the third lens;

[0010] a light transmission element, wherein the object-side surface of the light transmission element is a plane, and the image-side surface of the light transmission element is a plane;

[0011] The imaging system also satisfies: ;and ; Wherein, TTL is the total optical length of the imaging system, f is the total focal length of the imaging system, f L3 is the focal length of the third lens, f L4 is the focal length of the fourth lens, f G1 is the focal length of the first cemented lens group.

[0012] In some embodiments, the imaging system further satisfies: ; Among them, f L1 is the focal length of the first lens, f L2 is the focal length of the second lens, R S110 is the curvature radius of the image-side surface of the second lens.

[0013] In some embodiments, the imaging system further satisfies: ; Among them, R S109 is the radius of curvature of the second lens objective side, R S111 is the radius of curvature of the objective side of the third lens, R S112 is the curvature radius of the image side of the third lens, R S113 is the curvature radius of the image-side surface of the fourth lens.

[0014] In some embodiments, the second cemented lens group includes a first flat glass, a second flat glass, and a third flat glass sequentially arranged from the object side to the image side.

[0015] In some embodiments, the optical axis includes a first sight segment, a turning segment, and a second sight segment connected in sequence from the object side to the image side, and the angle between the extension direction of the first sight segment and the extension direction of the second sight segment is an acute angle.

[0016] In some embodiments, the second cemented lens group further has a first reflecting plane and a second reflecting plane respectively located at both ends of the turning section, the first reflecting plane is used to receive light passing through the object side surface of the second cemented lens group and reflect it toward the second reflecting plane, and the second reflecting plane is used to receive light reflected from the first reflecting plane and reflect it toward the image side surface of the second cemented lens group.

[0017] In some embodiments, the second cemented lens group includes a first prism, a second prism, and a third prism arranged in sequence from the object side to the image side, wherein the object-side surface of the second lens is adjacent to the image-side surface, the first reflection plane is located on the second lens and is adjacent to the object-side surface of the second lens, the object-side surface of the third lens is adjacent to the image-side surface, and the second reflection plane is located on the third lens and is adjacent to the object-side surface of the third lens.

[0018] In some embodiments, the light transmission element includes a fourth prism and a fifth prism arranged in sequence from the object side to the image side, and a dichroic film layer located between the fourth prism and the fifth prism, the dichroic film layer is used to transmit the first light and reflect the second light, and the fourth prism also has a dichroic side for transmitting the second light.

[0019] In some embodiments, the light-splitting side is arranged obliquely with respect to the optical axis.

[0020] In summary, this application is conditional By constraining the total optical length of the imaging system, the length of the lens barrel can be effectively controlled, so that the electronic endoscope lens of this patent can be designed in a miniaturized manner, and the focal length of the imaging system can be controlled within a certain range. It can be matched with the aperture to effectively control the field of view. By constraining the lens parameters of the first cemented lens group in the imaging system and selecting a combination of glass materials with different dispersion characteristics, axial chromatic aberration can be effectively corrected. The cemented lens is more compact than an equivalent separate design and reduces the number of independent lens elements and related mechanical fixing structures, which helps to improve the feasibility of processing. In addition, since the imaging system provided by the present application does not involve special-shaped lenses, the lens processing difficulty is reduced, facilitating production.

[0021] According to another aspect of the present application, the present application further provides an endoscope, comprising:

[0022] A mirror tube having a light inlet and a light outlet;

[0023] As the above-mentioned imaging system, the imaging system is installed in the mirror tube;

[0024] a first window lens, located on the object side of the imaging system and used to seal the light inlet of the lens tube;

[0025] A second window lens is located on the image side of the imaging system and is used to close the light outlet of the lens tube;

[0026] The photosensitive component is placed on the image side of the second window lens.

[0027] The endoscope provided by this application has at least the following advantages:

[0028] 1. The imaging system of this endoscope can realize multi-channel and detect smaller details with high resolution;

[0029] 2. The imaging system solution of this endoscope not only meets the requirements of excellent image quality, but also enhances the manufacturability of the lens;

[0030] 3. The imaging system of the endoscope can be miniaturized;

[0031] 4. The endoscope of this application is designed to have a minimum line width recognition accuracy of 2.5um, which greatly meets the current accuracy requirements of medical endoscopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic structural diagram of an imaging system in one embodiment provided in this application;

[0033] Figure 2 for Figure 1 Schematic diagram of the optical path of the imaging system shown;

[0034] Figure 3A is an optical transfer function curve diagram of the optical design of the imaging system according to the first embodiment of the present application;

[0035] Figure 3B This is an optical transfer function curve diagram of the optical design of the imaging system according to the second embodiment of the present application;

[0036] Figure 3C This is an optical transfer function curve diagram according to the optical design of the imaging system in Example 3 of the present application;

[0037] Figure 4 This is a schematic structural diagram of the imaging system in the fourth embodiment of the present application;

[0038] Figure 5 Based on Figure 4 Provide optical transfer function graphs of the optical design of the imaging system;

[0039] Figure 6 This is a schematic structural diagram of the imaging system in Example 5 of the present application;

[0040] Figure 7 Based on Figure 6Provide optical transfer function graphs of the optical design of the imaging system;

[0041] Figure 8 This is a schematic structural diagram of the imaging system in Example 6 of the present application;

[0042] Figure 9 Based on Figure 8 Provide optical transfer function graphs of the optical design of the imaging system;

[0043] Figure 10 This is a structural diagram of the imaging system in Example 7 of the present application.

[0044] Reference numerals:

[0045] P1, first window lens; P2, light transmission element; P3, second window lens; P4, first flat lens; P5, second flat lens; P6, third flat lens; L1, first lens; L2, second lens; L3, third lens; L4, fourth lens; G1, first cemented lens group; G2, second cemented lens group. DETAILED DESCRIPTION

[0046] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0048] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0049] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0050] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0051] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0052] See also Figure 1 and Figure 2 , Figure 1 This is a schematic structural diagram of an imaging system in one embodiment provided in this application. Figure 2 for Figure 1Schematic diagram of the optical path of the imaging system shown. The imaging system includes a first window lens P1, a first lens L1, a second cemented lens group G2, a second lens L2, a first cemented lens group G1, a light transmission element P2, and a second window lens P3, arranged in order from the object side to the image side. The first lens L1 has negative refractive power, with a flat object-side surface and a concave image-side surface. The second lens L2 has positive refractive power, with a convex object-side surface and a convex image-side surface. Both the object-side and image-side surfaces of the second cemented lens group G2 are flat. The first cemented lens group G1 includes a third lens L3 and a fourth lens L4, wherein the third lens L3 has positive focal power, the object-side surface and the image-side surface of the third lens L3 are both convex, the fourth lens L4 has negative focal power, the object-side surface of the fourth lens L4 is concave, and the image-side surface is convex, the image-side surface of the third lens L3 is cemented to the object-side surface of the fourth lens L4, the object-side surface and the image-side surface of the light transmission element P2 are both flat, the first window lens P1 and the second window lens P3 are both flat glass, and the imaging system further satisfies and , where TTL is the total optical length of the imaging system, f is the total focal length of the imaging system, and f L3 is the focal length of the third lens L3, f L4 is the focal length of the fourth lens L4, f G1 is the focal length of the first cemented lens group G1. Preferably, the imaging system satisfies and .

[0053] Optionally, in some embodiments provided herein, the imaging system further satisfies: ; Among them, f L1 is the focal length of the first lens L1, f L2 is the focal length of the second lens L2, R S110 is the radius of curvature of the image-side surface of the second lens L2. Thus, by constraining the focal lengths of the first lens L1 and the second lens L2, as well as their surface shapes, the above conditional expression ensures a reasonable spacing between the first lens L1 and the second lens L2, which helps control the overall length of the imaging system while ensuring imaging performance. Preferably, the imaging system satisfies: .

[0054] Optionally, in some embodiments provided herein, the imaging system further satisfies: ; Among them, R S109 is the radius of curvature of the object side of the second lens L2, R S111 is the radius of curvature of the object side of the third lens L3, R S112is the curvature radius of the image side of the third lens L3, R S113 is the radius of curvature of the image-side surface of the fourth lens L4. Thus, by constraining the radius of curvature of the image-side surface of the second lens L2 and the radius of curvature of each surface on the optical axis of the first cemented lens group G1, it is beneficial to improve the sensitivity of the imaging system to aberrations, thereby ensuring imaging quality. Preferably, the imaging system satisfies: .

[0055] Some specific but non-limiting examples of the above-mentioned embodiments of the present application are described in more detail below with reference to the accompanying drawings. For ease of description, in the following embodiments, S101 represents the object-side surface of the first window lens P1, S102 represents the image-side surface of the first window lens P1, S103 represents the object-side surface of the first lens L1, S104 represents the image-side surface of the first lens L1, S105 represents the object-side surface of the first flat plate lens P4, S106 represents the image-side surface of the first flat plate lens P4, S107 represents the image-side surface of the second flat plate lens P5, S108 represents the image-side surface of the third flat plate lens P6, and S109 represents the object-side surface of the second lens L2. S110 represents the image-side surface of the second lens L2, S111 represents the object-side surface of the third lens L3, S112 represents the image-side surface of the third lens L3, S113 represents the image-side surface of the fourth lens L4, S114 represents the object-side surface of the light transmission element P2, S115 represents the image-side surface of the light transmission element P2, S116 represents the object-side surface of the second window lens P3, S117 represents the image-side surface of the second window lens P3, and S118 represents the light-receiving surface of the photosensitive component, which coincides with the image plane of the imaging system.

[0056] Example 1

[0057] The curvature radius R, center thickness Tc, refractive index Nd, and Abbe constant Vd of each lens of the imaging system in this embodiment meet the conditions listed in Table 1.

[0058] Table 1 Optical parameters of the imaging system in Example 1

[0059]

[0060] In this embodiment 1, the first lens L1 in the imaging process is a meniscus lens with a focal length of f L1 The second lens L2 in the imaging system is a biconvex lens with a focal length of f L2 The image side surface S110 of the second lens L2 is convex and has a curvature radius of R S110 , f L1 、f L2 、R S110 Satisfy between: , the total focal length of the imaging system is f, the total optical length of the imaging system is TTL, and the relationship between f and TTL satisfies: The third lens L3 in the imaging system is a biconvex lens with a focal length of f L3 , the fourth lens L4 in the imaging system is a meniscus lens with a focal length of f L4 , the focal length of the first cemented lens group G1 in the imaging system is f G1 , f L3 、f L4 、f G1 Satisfy between: .

[0061] The object side surface S109 of the second lens L2 in the imaging system is a convex surface with a curvature radius of R S109 , the object side surface S111 of the third lens L3 in the imaging system is a convex surface with a curvature radius of R S111 , the image side surface S112 of the third lens L3 in the imaging system is a convex surface and the curvature radius of the surface is R S112 In the imaging system, the image side surface S113 of the fourth lens L4 is a convex surface and the curvature radius of the surface is R S113 , R S109 、R S111 、R S112 、R S113 Satisfy between: .

[0062] Example 2

[0063] The curvature radius R, center thickness Tc, refractive index Nd, and Abbe constant Vd of each lens of the imaging system in this embodiment meet the conditions listed in Table 2.

[0064] Table 2 Optical parameters of the imaging system in Example 2

[0065]

[0066] In this embodiment 2, the first lens L1 in the imaging system is a meniscus lens with a focal length of f L1 The second lens L2 in the imaging system is a biconvex lens with a focal length of f L2 The image side surface S110 of the second lens L2 is convex and has a curvature radius of R S110 , f L1 、f L2 、R S110 Satisfy between: The total focal length of the imaging system is f, the total optical length of the imaging system is TTL, and the relationship between f and TTL satisfies: The third lens L3 in the imaging system is a biconvex lens with a focal length of f L3 , the fourth lens L4 in the imaging system is a meniscus lens with a focal length of f L4, the focal length of the first cemented lens group G1 in the imaging system is f G1 , f L3 、f L4 、f G1 Satisfy between: ;

[0067] The object side surface S109 of the second lens L2 in the imaging system is a convex surface with a curvature radius of R S109 , the object side surface S111 of the third lens L3 in the imaging system is a convex surface with a curvature radius of R S111 , the image side surface S112 of the third lens L3 in the imaging system is a convex surface and the curvature radius of the surface is R S112 In the imaging system, the image side surface S113 of the fourth lens L4 is a convex surface and the curvature radius of the surface is R S113 , R S109 、R S111 、R S112 、R S113 Satisfy between: .

[0068] Example 3

[0069] The curvature radius R, center thickness Tc, refractive index Nd, and Abbe constant Vd of each lens of the imaging system in this embodiment meet the conditions listed in Table 3.

[0070] Table 3 Optical parameters of the imaging system in Example 3

[0071]

[0072] In this embodiment 3, the first lens L1 in the imaging system is a meniscus lens with a focal length of f L1 The second lens L2 in the imaging system is a biconvex lens with a focal length of f L2 The image side surface S110 of the second lens L2 is convex and has a curvature radius of R S110 , f L1 、f L2 、R S110 Satisfy between: The total focal length of the imaging system is f, the total optical length of the imaging system is TTL, and the relationship between f and TTL satisfies: The third lens L3 in the imaging system is a biconvex lens with a focal length of f L3 , the fourth lens L4 in the imaging system is a meniscus lens with a focal length of f L4 , the focal length of the first cemented lens group G1 in the imaging system is f G1 , f L3 、f L4 、f G1 Satisfy between: ;

[0073] The object side surface S109 of the second lens L2 in the imaging system is a convex surface with a curvature radius of R S109 , the object side surface S111 of the third lens L3 in the imaging system is a convex surface with a curvature radius of R S111 , the image side surface S112 of the third lens L3 in the imaging system is a convex surface and the curvature radius of the surface is R S112 In the imaging system, the image side surface S113 of the fourth lens L4 is a convex surface and the curvature radius of the surface is R S113 , R S109 、R S111 、R S112 、R S113 Satisfy between: .

[0074] In summary, the technical indicators satisfied by the imaging systems in Examples 1 to 3 of the present application are shown in Table 4, where WFNO represents the aperture value of the imaging system, FOV represents the field of view angle of the imaging system, TTL represents the total optical length of the imaging system, and I MTF Indicates the MTF value of the imaging system at 200lp / mm, f represents the overall focal length of the imaging system, f L1 represents the focal length of the first lens L1, f L2 represents the focal length of the second lens L2, f L3 represents the focal length of the third lens L3, f L4 represents the focal length of the fourth lens L4, f G1 represents the focal length of the first cemented lens group G1.

[0075] Table 4: Some technical indicators of the imaging system in Examples 1 to 3

[0076]

[0077] The optical transfer function is generally used to evaluate the imaging quality, and the diffraction limit is the highest resolution limit that the imaging system can achieve under ideal conditions (no aberration).

[0078] See also Figures 3A to 3C , Figures 3A to 3C The following are optical transfer function (MTF) curves of the imaging systems in Examples 1 to 3 of this patent, respectively. As can be seen from the figures, the curves are smooth and slowly decrease in the entire field of view, and all curves are close to the diffraction limit and tend to the highest resolution limit, indicating that the imaging quality is high. The design of this patent can distinguish a minimum line width of 2.5um. When applied to medical products, it has obvious advantages in the detection of tiny blood vessels and details.

[0079] See also Figure 1 、 Figure 2 、 Figure 4、 Figure 6 and Figure 8 Optionally, in some embodiments provided herein, the second cemented lens group includes a first flat lens P4, a second flat lens P5, and a third flat lens P6, arranged sequentially from the object side to the image side. Thus, the three flat lenses cemented together to form the second cemented lens group help reduce light loss during transmission. The second cemented lens G2 can better guide light to the second lens L2, reducing stray light.

[0080] See also Figure 10 , Figure 10 This is a schematic diagram of the structure of an imaging system in another embodiment provided by the present application. Optionally, in some embodiments provided by the present application, the optical axis includes a first line of sight segment, a turning segment, and a second line of sight segment, which are connected in sequence from the object side to the image side. The angle e between the extension direction of the first line of sight segment and the extension direction of the second line of sight segment is an acute angle. Specifically, in one embodiment, the angle e is 30°. In this way, the angle of view is shifted while the insertion direction of the endoscope remains unchanged. The design is flexible, the degree of freedom of the endoscope's field of view is more controllable, and since there is no need to rotate the endoscope tube to adjust the angle of view, the increase in the surgical incision area is avoided.

[0081] like Figure 10 As shown, Figure 10 This is a schematic diagram of the structure of the imaging system in Example 7. Specifically, in some embodiments provided in this application, the second cemented lens group further has a first reflection plane S1061 and a second reflection plane S1071, respectively located at both ends of the turning section. The first reflection plane S1061 is used to receive light passing through the object-side surface of the second cemented lens group G2 and reflect it toward the second reflection plane S1071. The second reflection plane S1071 is used to receive light reflected from the first reflection plane S1061 and reflect it toward the image-side surface S1081 of the second cemented lens group G2. In this way, by arranging two reflection planes to achieve the above-mentioned perspective shifting function, the optical path is simple, the actual occupied space is also small, which facilitates the arrangement in the endoscope and helps to ensure the integrity of the imaging picture.

[0082] like Figure 10As shown, further, in order to realize the optical path, in one embodiment provided in the present application, the second cemented lens group G2 includes a first prism, a second prism and a third prism arranged in sequence from the object side to the image side, specifically, the three prisms are all quadrilateral prisms, the cementing surface of the first prism and the second prism is S106, and the surface S106 corresponds to the image side surface of the first prism and the object side surface of the second prism, and the cementing surface of the second prism and the third prism is S107, and the surface S107 corresponds to the image side surface of the second prism and the object side surface of the third prism, wherein the object side surface of the second prism is adjacent to the image side surface, the first reflection plane S1061 is located in the second prism and adjacent to the object side surface of the second prism, the object side surface of the third prism is adjacent to the image side surface, and the second reflection plane S1071 is located in the third prism and adjacent to the object side surface of the third prism. In this way, the turning optical path is realized by gluing prisms. On the one hand, the transmission of light by means of the glued prisms is conducive to reducing light loss and stray light. On the other hand, the prism combination method also reduces the difficulty of realizing the optical path and reduces the design cost of the imaging system. Since there is no need to customize special lenses for realizing the turning optical path, the use of special-shaped lenses is avoided, and the production cost of the endoscope is also reduced. It is understandable that in other embodiments, the first reflection plane and the second reflection plane can also be located on the same prism, that is, the turning section of the optical axis is completely located in the prism. For example, the first reflection plane and the second reflection plane are a pair of surfaces arranged opposite to each other on a quadrangular prism, and the other pair of surfaces are the object side and the image side respectively; or the first reflection plane can also be located on the first prism, which will not be described in detail here.

[0083] Please refer again Figure 1 Optionally, in one embodiment provided in the present application, the light transmission element P2 is a complete quadrangular prism, which is only used to transmit light to reduce light loss and stray light.

[0084] See also Figure 4 , Figure 4This is a structural diagram of the imaging system in Example 4. Optionally, in an embodiment provided in the present application, the light transmission element P2 includes a fourth prism and a fifth prism arranged in sequence from the object side to the image side, and a dichroic film layer located between the fourth prism and the fifth prism. The dichroic film layer is used to transmit the first light and reflect the second light. The fourth prism also has a dichroic side for transmitting the second light. In this embodiment, the second light is light in a wide spectral band, and a photosensitive component is arranged on the dichroic side. By screening the spectrum, the influence of dispersion factors on the imaging quality is avoided. Specifically, in this embodiment, the light transmission element P2 is a prism A. The angle a in the prism splitting (the angle between the splitting surface S119 and the normal of the surface S1911) is designed to be 45° in this embodiment. The light passes through the lens from the object side and is incident vertically along the optical axis to the prism A. The light turns at the surface S119 of the prism A, which can make 90% of the light in the 400nm~900nm band be incident on the image surface S1911. The image surface S1911 is the splitting side of the light transmission element P2. The surface S119 in the light transmission element P2 is generally coated to achieve wide-spectrum reflection. This design can effectively shorten the length of the lens in the direction of the optical axis and achieve miniaturization requirements within a limited cavity space. Figure 5 As shown, Figure 5 This is the optical transfer function curve of the imaging system. As can be seen from the figure, each field of view curve decreases slowly and smoothly, and is close to the diffraction limit as a whole, indicating that the system has excellent image quality and a clear picture.

[0085] See also Figure 6 , Figure 6 This is a structural diagram of the imaging system in Example 5. In one embodiment provided in the present application, the light transmission element P2 is a prism B, which is composed of two triangular prisms glued together and has two light-emitting directions, corresponding to an image side and a splitting side. The image side is provided with a photosensitive component with a photosensitive surface S1201, and the splitting side is provided with a photosensitive component with a photosensitive surface S1202. In this embodiment, the splitting surface of the prism B is S120. The specific optical path in prism B is as follows: light passes through the lens from the object side and is incident vertically along the optical axis onto prism B. Surface S120 is the direct beam splitting surface of prism B. In this embodiment, the angle b in prism beam splitting (the angle between the object side surface S114 of the optical transmission element P2 and the beam splitting surface S120) is designed to be 45°. After the light reaches surface S120, half of the light is transmitted to image surface S1201 on surface S120, and the other half is reflected to image surface S1202 on surface S120. Here, no distinction is made between wavelength bands, and dual-sensor imaging can still be achieved, showing high-quality imaging. Figure 7 As shown in , each field of view curve decreases slowly and smoothly, and is close to the diffraction limit as a whole, indicating that the system's resolution has reached its peak and the clarity is good.

[0086] See also Figure 8 , Figure 8 This is a structural diagram of the imaging system in Example 6. Furthermore, in an embodiment provided in the present application, the splitting side of the light transmission element P2 is arranged at an angle to the optical axis. The optical transmission prism in this embodiment is a prism C, which is composed of a pentagonal prism and a quadrilateral prism glued together, and has two light-emitting directions, corresponding to an image side and a splitting side. The image side is provided with a photosensitive component with a photosensitive surface S1211, and the splitting side is provided with a photosensitive component with a photosensitive surface S1212. In this embodiment, the splitting surface of the prism C is S121. The specific optical path in prism C is as follows: light passes through the lens from the object side and is incident vertically along the optical axis onto prism C. The c angle (the angle between the normal of the image plane S1212 and the beam splitting surface S121) in prism C is 55°, and the d angle (the angle between the beam splitting surface S121 and the optical axis) is 70°. The S121 surface is separated in prism C by the c and d angles. Half of the light passes directly through the S121 surface to the image plane S1211, and the other half of the light is reflected from the S121 surface to the image plane S1212. This design can achieve higher reflection efficiency, reaching more than 95% on the S121 surface, and achieving higher image effects. Figure 9 As shown in , each field of view curve decreases slowly and smoothly, and is close to the diffraction limit as a whole, indicating that the system's resolution has reached its peak and the clarity is good.

[0087] It is worth noting that in Figure 3A 、 Figure 3B 、 Figure 3C 、 Figure 5 、 Figure 7 、 Figure 9 In this application, the MTF curves under multiple fields of view are selected, including the MTF curves under seven fields of view, namely 0 degrees, 13.50 degrees, 22.50 degrees, 30.00 degrees, 38.50 degrees, 45.00 degrees, and 46.50 degrees in the meridian and sagittal directions respectively.

[0088] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0089] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. An imaging system, characterized in that: Including the following arranged in sequence from the object side to the image side along the optical axis: A first lens having negative optical power, wherein the object-side surface of the first lens is flat and the image-side surface is concave; a second cemented lens group, wherein the object-side surface of the second cemented lens group is a plane and the image-side surface is a plane; a second lens having positive optical power, wherein the object-side surface and the image-side surface of the second lens are convex; a first cemented lens group, comprising a third lens and a fourth lens, wherein the third lens has positive power, the object-side surface of the third lens is convex, and the image-side surface of the third lens is convex; the fourth lens has negative power, the object-side surface of the fourth lens is concave, and the image-side surface of the fourth lens is convex; and the object-side surface of the fourth lens is cemented to the image-side surface of the third lens; a light transmission element, wherein the object-side surface of the light transmission element is a plane, and the image-side surface of the light transmission element is a plane; The imaging system satisfies: ;and ; Wherein, TTL is the total optical length of the imaging system, f is the total focal length of the imaging system, f L3 is the focal length of the third lens, f L4 is the focal length of the fourth lens, f G1 is the focal length of the first cemented lens group.

2. The imaging system according to claim 1, wherein: The imaging system also satisfies: ; Among them, f L1 is the focal length of the first lens, f L2 is the focal length of the second lens, R S110 is the curvature radius of the image-side surface of the second lens.

3. The imaging system according to claim 1, wherein: The imaging system also satisfies: ; Among them, R S109 is the radius of curvature of the second lens objective side, R S111 is the radius of curvature of the objective side of the third lens, R S112 is the curvature radius of the image side of the third lens, R S113 is the curvature radius of the image-side surface of the fourth lens.

4. The imaging system according to any one of claims 1 to 3, wherein: The second cemented lens group includes a first flat lens, a second flat lens, and a third flat lens arranged in sequence from the object side to the image side.

5. The imaging system according to any one of claims 1 to 3, wherein: The optical axis includes a first sight segment, a turning segment, and a second sight segment connected in sequence from the object side to the image side, and the angle between the extension direction of the first sight segment and the extension direction of the second sight segment is an acute angle.

6. The imaging system according to claim 5, wherein: The second cemented lens group also has a first reflection plane and a second reflection plane respectively located at both ends of the turning section, the first reflection plane is used to receive light passing through the object side surface of the second cemented lens group and reflect it toward the second reflection plane, and the second reflection plane is used to receive light reflected from the first reflection plane and reflect it toward the image side surface of the second cemented lens group.

7. The imaging system according to claim 6, wherein: The second cemented lens group includes a first prism, a second prism and a third prism arranged in sequence from the object side to the image side, wherein the object side surface of the second prism is adjacent to the image side surface, the first reflection plane is located in the second prism and adjacent to the object side surface of the second prism, the object side surface of the third prism is adjacent to the image side surface, and the second reflection plane is located in the third prism and adjacent to the object side surface of the third prism.

8. The imaging system according to any one of claims 1 to 3, wherein: The light transmission element includes a fourth prism and a fifth prism arranged in sequence from the object side to the image side, and a dichroic film layer located between the fourth prism and the fifth prism. The dichroic film layer is used to transmit the first light and reflect the second light. The fourth prism also has a dichroic side for transmitting the second light.

9. The imaging system according to claim 8, wherein: The light splitting side is arranged obliquely to the optical axis.

10. An endoscope, characterized in that: include: A mirror tube having a light inlet and a light outlet; The imaging system according to any one of claims 1 to 9, wherein the imaging system is installed in the mirror tube; a first window lens, located on the object side of the imaging system and used to seal the light inlet of the lens tube; A second window lens is located on the image side of the imaging system and is used to close the light outlet of the lens tube; The photosensitive component is placed on the image side of the second window lens.

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