Endoscope optical system, objective lens module, and endoscope

Abstract

The application relates to an endoscope optical system, an objective lens module and an endoscope. The endoscope optical system comprises a first lens with negative focal power, the image side surface of the first lens is concave at the near optical axis; a second lens with positive focal power, the object side surface of the second lens is convex at the near optical axis; a third lens with positive focal power, the image side surface of the third lens is convex at the near optical axis; a fourth lens with negative focal power, the object side surface of the fourth lens is concave at the near optical axis; and the endoscope optical system satisfies 4.08 <= TTL / f <= 4.52. The endoscope optical system can balance small size design and good imaging quality.

Description

Technical Field

[0001] This application relates to the field of endoscope technology, and in particular to an endoscope optical system, objective lens module and endoscope. Background Technology

[0002] With the rapid development of medical equipment, endoscopes are increasingly widely used in the medical field. Endoscopes can be inserted into a user's body to obtain images of lesions, facilitating diagnosis and treatment. The imaging quality of an endoscope directly impacts the accuracy of diagnosis and treatment. In related technologies, increasing the number of lenses in the endoscope's optical system is often used to improve imaging quality, but this can easily lead to an excessively large endoscope, potentially causing injury to the user. Furthermore, it is difficult to simultaneously achieve both small size and high imaging quality in endoscopes developed in these technologies. Summary of the Invention

[0003] Therefore, it is necessary to address the problem that endoscopes in related technologies cannot simultaneously achieve small size and high imaging quality by providing an endoscope optical system, objective lens module, and endoscope.

[0004] An endoscopic optical system, comprising, along the optical axis from the object side to the image side, the following components:

[0005] A first lens with negative optical power, wherein the image-side surface of the first lens is concave near the optical axis;

[0006] A second lens with positive optical power, wherein the object side of the second lens is convex near the optical axis;

[0007] A third lens with positive optical power, wherein the image-side surface of the third lens is convex near the optical axis;

[0008] A fourth lens with negative optical power, wherein the object side of the fourth lens is concave near the optical axis;

[0009] Furthermore, the endoscopic optical system satisfies the following condition:

[0010] 4.08≤TTL / f≤4.52;

[0011] Where TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the endoscope optical system, i.e., the total optical length of the endoscope optical system, and f is the focal length of the endoscope optical system.

[0012] In the aforementioned endoscopic optical system, the first lens has negative optical power, and its image-side surface is concave near the optical axis. This facilitates the collection of large-angle light rays by the first lens, thereby expanding the field of view of the endoscopic optical system and achieving wide-angle characteristics. The second lens has positive optical power, which helps correct distortions and other aberrations caused by the first lens when introducing large-angle light rays, thus improving the imaging quality of the endoscopic optical system. The third lens has positive optical power, and its image-side surface is convex near the optical axis, which helps converge light rays towards the image side, thus shortening the overall length of the endoscopic optical system. The fourth lens has negative optical power, and its object-side surface is concave near the optical axis, which helps to deflect light rays appropriately towards the imaging plane, thereby adjusting the incident angle of light rays on the imaging plane and increasing the size of the imaging plane, further improving the imaging quality of the endoscopic optical system. Meeting the above conditions facilitates the rational configuration of the TTL and f ratio, which not only shortens the overall length of the endoscope optical system, enabling a smaller size design, but also allows the endoscope optical system to effectively deflect light, improving its imaging quality. With the aforementioned optical power and surface characteristics, and meeting the above conditions, the endoscope optical system can achieve good imaging quality with four lenses, balancing small size and high imaging quality.

[0013] In one embodiment, the endoscopic optical system satisfies the following condition:

[0014] -0.9≤f1 / f≤-0.7;

[0015] Where f1 is the focal length of the first lens.

[0016] In one embodiment, the endoscopic optical system satisfies the following condition:

[0017] -9.9≤f4 / f3≤-1.7;

[0018] Where f4 is the focal length of the fourth lens and f3 is the focal length of the third lens.

[0019] In one embodiment, the endoscopic optical system satisfies the following condition:

[0020] 1.45≤Bf / f≤1.72;

[0021] Wherein, Bf is the distance on the optical axis from the image side of the fourth lens to the imaging surface of the endoscope optical system.

[0022] In one embodiment, the endoscopic optical system satisfies the following condition:

[0023] 1.6 ≤ f2 / f ≤ 2.4; where f2 is the focal length of the second lens; and / or,

[0024] 0.7≤f3 / f≤1.4; where f3 is the focal length of the third lens.

[0025] In one embodiment, the endoscopic optical system satisfies the following condition:

[0026] -3≤f2 / f1≤-1.5;

[0027] Where f2 is the focal length of the second lens and f1 is the focal length of the first lens.

[0028] In one embodiment, the endoscopic optical system satisfies the following condition:

[0029] 1.51mm -1 ≤FNO / TTL≤1.7mm -1 ;

[0030] Wherein, FNO is the aperture number of the endoscope optical system.

[0031] In one embodiment, the endoscopic optical system satisfies the following condition:

[0032] 0.05≤|R7 / R8|≤0.77; where R7 is the radius of curvature of the object-side surface of the fourth lens at the optical axis, and R8 is the radius of curvature of the image-side surface of the fourth lens at the optical axis; and / or,

[0033] 0.02≤|R4 / R5|≤1.44; where R4 is the radius of curvature of the image side of the second lens at the optical axis, and R5 is the radius of curvature of the object side of the third lens at the optical axis.

[0034] An objective lens module includes a photosensitive element and an endoscope optical system as described in any of the above embodiments, wherein the photosensitive element is disposed on the image side of the endoscope optical system.

[0035] An endoscope comprising the aforementioned objective lens module. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the endoscope optical system in the first embodiment.

[0037] Figure 2a This is an astigmatism curve of the endoscope optical system in the first embodiment.

[0038] Figure 2b This is a distortion curve of the endoscope optical system in the first embodiment.

[0039] Figure 2c This is a magnification chromatic aberration curve of the endoscope optical system in the first embodiment.

[0040] Figure 3 This is a schematic diagram of the endoscope optical system in the second embodiment.

[0041] Figure 4a This is an astigmatism curve of the endoscope optical system in the second embodiment.

[0042] Figure 4b This is a distortion curve of the endoscope optical system in the second embodiment.

[0043] Figure 4c This is a magnification chromatic aberration curve of the endoscope optical system in the second embodiment.

[0044] Figure 5 This is a schematic diagram of the endoscope optical system in the third embodiment.

[0045] Figure 6a This is an astigmatism curve of the endoscope optical system in the third embodiment.

[0046] Figure 6b This is a distortion curve of the endoscope optical system in the third embodiment.

[0047] Figure 6c This is a magnification chromatic aberration curve of the endoscope optical system in the third embodiment.

[0048] Figure 7 This is a schematic diagram of the endoscope optical system in the fourth embodiment.

[0049] Figure 8a This is an astigmatism curve of the endoscope optical system in the fourth embodiment.

[0050] Figure 8b This is a distortion curve of the endoscope optical system in the fourth embodiment.

[0051] Figure 8c This is a magnification chromatic aberration curve of the endoscope optical system in the fourth embodiment.

[0052] Figure 9 This is a schematic diagram of the endoscope optical system in the fifth embodiment.

[0053] Figure 10a This is an astigmatism curve of the endoscope optical system in the fifth embodiment.

[0054] Figure 10b This is a distortion curve of the endoscope optical system in the fifth embodiment.

[0055] Figure 10c This is a magnification chromatic aberration curve of the endoscope optical system in the fifth embodiment.

[0056] Figure 11This is a schematic diagram of the endoscope optical system in the sixth embodiment.

[0057] Figure 12a This is an astigmatism curve of the endoscope optical system in the sixth embodiment.

[0058] Figure 12b This is a distortion curve of the endoscope optical system in the sixth embodiment.

[0059] Figure 12c This is a magnification chromatic aberration curve of the endoscope optical system in the sixth embodiment.

[0060] Figure 13 This is a schematic diagram of the endoscope optical system in the seventh embodiment.

[0061] Figure 14a This is an astigmatism curve of the endoscope optical system in the seventh embodiment.

[0062] Figure 14b This is a distortion curve of the endoscope optical system in the seventh embodiment.

[0063] Figure 14c This is a magnification chromatic aberration curve of the endoscope optical system in the seventh embodiment. Detailed Implementation

[0064] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0065] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0066] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0067] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0068] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0069] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0070] Please see Figure 1 , Figure 1The diagram illustrates the structure of an endoscope optical system 100 in some embodiments of this application. The endoscope optical system 100 provided in this application can be applied to any applicable type of endoscope. The endoscope optical system 100 can adjust the light incident on the endoscope, enabling the light to form a clear image. In some embodiments of this application, the endoscope optical system 100 includes, along the optical axis from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, and a fourth lens L4. Each of the first lens L1, second lens L2, third lens L3, and fourth lens L4 includes an object-side surface facing the object side and an image-side surface facing the image side. The first lens L1, second lens L2, third lens L3, and fourth lens L4 can be coaxially arranged, and the common axis of all lenses in the endoscope optical system 100 is the optical axis of the endoscope optical system 100. In some embodiments, the endoscopic optical system 100 may further include an imaging surface 110 located on the image side of the fourth lens L4. Light rays incident on the endoscopic optical system 100 can be incident on the imaging surface 110 after being adjusted by the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4. In this application, the object side of the endoscopic optical system 100 can be understood as the side of the endoscopic optical system 100 facing the object being photographed, such as the side facing the lesion area, and the image side of the endoscopic optical system 100 can be understood as the side where the imaging surface 110 of the endoscopic optical system 100 is located.

[0071] In some embodiments, the first lens L1 has negative optical power, and its image-side surface is concave near the optical axis. The second lens L2 has positive optical power, and its object-side surface is convex near the optical axis. The third lens L3 has positive optical power, and its image-side surface is convex near the optical axis. The fourth lens L4 has negative optical power, and its object-side surface is concave near the optical axis. It should be noted that, in this application, describing the surface shape of a lens near the optical axis can be understood as the surface shape of the portion of the lens corresponding to the area traversed by paraxial rays.

[0072] In the aforementioned endoscopic optical system 100, the first lens L1 has negative optical power, and its image-side surface is concave near the optical axis. This facilitates the collection of large-angle light rays by the first lens L1, thereby expanding the field of view of the endoscopic optical system 100 and achieving wide-angle characteristics. The second lens L2 has positive optical power, which helps correct distortions and other aberrations caused by the first lens L1 when introducing large-angle light rays, thus improving the imaging quality of the endoscopic optical system 100. The third lens L3 has positive optical power, and its image-side surface is convex near the optical axis. This helps converge light rays towards the image side, thus shortening the overall length of the endoscopic optical system 100. The fourth lens L4 has negative optical power, and its object-side surface is concave near the optical axis. This helps to properly deflect light rays towards the imaging surface 110, thereby adjusting the incident angle of light rays on the imaging surface 110 and increasing the size of the imaging surface 110, further improving the imaging quality of the endoscopic optical system 100.

[0073] Furthermore, in some embodiments, the endoscope optical system 100 satisfies the condition: 4.08 ≤ TTL / f ≤ 4.52; where TTL is the distance on the optical axis from the object surface of the first lens L1 to the imaging surface of the endoscope optical system 100, i.e., the total optical length of the endoscope optical system 100, and f is the focal length of the endoscope optical system 100. Satisfying the above condition facilitates the rational configuration of the ratio of TTL to f, which is beneficial for shortening the total length of the endoscope optical system 100, achieving a small-size design, and also for enabling the endoscope optical system 100 to effectively deflect light, thereby improving the imaging quality of the endoscope optical system 100.

[0074] Having the aforementioned optical power and surface features, and satisfying the aforementioned conditions, the endoscope optical system 100 can achieve good imaging quality with a relatively small number of four lenses, can balance small size and high imaging quality, and can achieve wide-angle characteristics, thus meeting the wide-range imaging requirements of endoscopes.

[0075] In some embodiments, the endoscope optical system 100 is provided with an aperture stop 120, which may be disposed between the second lens L2 and the third lens L3. The central placement of the aperture stop 120 allows the endoscope optical system 100 to achieve a small size while still having sufficient light intake, thereby improving the imaging quality of the endoscope optical system 100.

[0076] In some embodiments, the endoscope optical system 100 further includes a protective glass 130 disposed between the fourth lens L4 and the imaging surface 110. When the endoscope optical system 100 is applied in an objective lens module, the protective glass 130 protects the photosensitive element located on the imaging surface 110 in the objective lens module. In some embodiments, the endoscope optical system 100 further includes a filter 140 disposed between the fourth lens L4 and the protective glass 130. The filter 140 filters out interfering light, preventing interfering light from reaching the imaging surface 110 and affecting normal imaging. For example, the filter 140 can be an infrared cut-off filter, used to block light in the near-infrared region that may be sensed by the photosensitive element. Of course, the filter 140 can also be disposed between any two lenses in the endoscope optical system 100.

[0077] In some embodiments, the object-side and image-side surfaces of each lens in the endoscope optical system 100 are aspherical, and the surface shapes of the object-side and image-side surfaces of each lens may differ near the optical axis and around the circumference. The use of aspherical structures can improve the flexibility of lens design, effectively correct spherical aberration, and improve image quality, enabling the endoscope optical system 100 to obtain good image quality with a smaller number of lenses.

[0078] In some embodiments, each lens in the endoscope optical system 100 may be made of plastic. Using plastic lenses can reduce the weight of the endoscope optical system 100 and lower production costs. Furthermore, each lens may be made of any suitable biocompatible plastic such as polymer resin, which helps reduce the risk of injury to the user when the endoscope optical system 100 is used with an endoscope.

[0079] In some embodiments, the endoscope optical system 100 satisfies the condition: -0.9 ≤ f1 / f ≤ -0.7; where f1 is the focal length of the first lens L1. When the above condition is satisfied, the ratio of the focal length of the first lens L1 to the focal length of the endoscope optical system 100 can be reasonably configured, enabling the first lens L1 to effectively collect large-angle light, thereby facilitating the achievement of wide-angle characteristics. Simultaneously, it prevents excessive deflection of the first lens L1 when introducing large-angle light, which helps suppress aberrations such as distortion and improves the imaging quality of the endoscope optical system 100.

[0080] In some embodiments, the endoscopic optical system 100 satisfies the condition: -9.9 ≤ f4 / f3 ≤ -1.7; where f4 is the focal length of the fourth lens L4 and f3 is the focal length of the third lens L3. When the above condition is satisfied, the ratio of the focal lengths of the fourth lens L4 and the third lens L3 can be reasonably configured, ensuring that the optical power of the fourth lens L4 is not too strong and the optical power of the third lens L3 is not too weak. This allows the third lens L3 and the fourth lens L4 to work together to smoothly converge light onto the imaging surface 110, while also helping to correct various aberrations in the off-axis field of view and improve the imaging quality of the endoscopic optical system 100.

[0081] In some embodiments, the endoscope optical system 100 satisfies the condition: 1.45 ≤ Bf / f ≤ 1.72; where Bf is the distance on the optical axis from the image-side surface of the fourth lens L4 to the imaging surface 110 of the endoscope optical system 100. Satisfying the above condition allows for a reasonable configuration of the ratio of the back focal length to the focal length of the endoscope optical system 100, ensuring sufficient back focal space for light transition and adequate focusing space to meet focusing requirements. It also facilitates the assembly of the endoscope optical system 100 with the photosensitive element in the objective lens module.

[0082] In some embodiments, the endoscope optical system 100 satisfies the condition: 1.6 ≤ f2 / f ≤ 2.4; where f2 is the focal length of the second lens L2. By rationally configuring the ratio of the focal length of the second lens L2 to the focal length of the endoscope optical system 100, the optical power of the second lens L2 is not excessive, and light rays can transition smoothly through the second lens L2. This facilitates the correction of aberrations such as coma in the off-axis field of view, thereby improving the imaging quality of the endoscope optical system 100.

[0083] In some embodiments, the endoscope optical system 100 satisfies the condition: 0.7 ≤ f3 / f ≤ 1.4; where f3 is the focal length of the third lens L3. When the above condition is satisfied, the ratio of the focal length of the third lens L3 to the focal length of the endoscope optical system 100 can be reasonably configured, so that the third lens L3 has sufficient optical power and can effectively converge light, which is beneficial to compressing the overall length of the endoscope optical system 100 and realizing a small-size design.

[0084] In some embodiments, the endoscopic optical system 100 satisfies the condition: -3 ≤ f2 / f1 ≤ -1.5; where f2 is the focal length of the second lens L2 and f1 is the focal length of the first lens L1. When the above condition is satisfied, the ratio of the focal length of the second lens L2 to the focal length of the first lens L1 can be reasonably configured, allowing for a proper combination of the first lens L1 and the second lens L2. This not only introduces large-angle light to achieve wide-angle characteristics but also helps suppress aberrations such as distortion and coma, thereby improving the imaging quality of the endoscopic optical system 100.

[0085] In some embodiments, the endoscopic optical system 100 satisfies the condition: 1.51 mm -1 ≤FNO / TTL≤1.7mm -1 Where FNO is the aperture number of the endoscope optical system 100. When the above conditions are met, it is beneficial to reduce the effective aperture and total length of the endoscope optical system 100, thereby reducing the size of the endoscope optical system 100 and achieving a small-size design. At the same time, it is also beneficial to ensure that the aperture of the endoscope optical system 100 is not too small, thus ensuring that the endoscope optical system 100 obtains sufficient light and has good imaging quality.

[0086] In some embodiments, the endoscopic optical system 100 satisfies the condition: 0.05 ≤ |R7 / R8| ≤ 0.77; where R7 is the radius of curvature of the object-side surface of the fourth lens L4 at the optical axis, and R8 is the radius of curvature of the image-side surface of the fourth lens L4 at the optical axis. When the above condition is satisfied, the ratio of the radii of curvature of the object-side surface to the image-side surface of the fourth lens L4 at the optical axis can be reasonably configured, allowing the fourth lens L4 to smoothly transition light to the imaging surface 110. This is beneficial for correcting aberrations in the endoscopic optical system 100 and for reasonably adjusting the incident angle of light on the imaging surface 110, thereby improving the imaging quality of the endoscopic optical system 100.

[0087] In some embodiments, the endoscopic optical system 100 satisfies the condition: 0.02 ≤ |R4 / R5| ≤ 1.44; where R4 is the radius of curvature of the image-side surface of the second lens L2 at the optical axis, and R5 is the radius of curvature of the object-side surface of the third lens L3 at the optical axis. When the above condition is satisfied, the ratio of the radii of curvature of the image-side surface of the second lens L2 to the object-side surface of the third lens L3 at the optical axis, combined with the design of the aperture 120 positioned between the second lens L2 and the third lens L3, facilitates a smooth transition of light between the second lens L2 and the third lens L3 and fills the aperture 120. This helps correct aberrations in the endoscopic optical system 100 and increases the amount of light entering the endoscopic optical system 100, thereby improving the imaging quality of the endoscopic optical system 100.

[0088] In some embodiments, the endoscope optical system 100 satisfies the condition: 1.4 ≤ T12 / T23 ≤ 6.3; where T12 is the distance on the optical axis from the image-side surface of the first lens L1 to the object-side surface of the second lens L2, and T23 is the distance on the optical axis from the image-side surface of the second lens L2 to the object-side surface of the third lens L3. Satisfying this condition allows for a reasonable configuration of the ratio of the air gap between the first lens L1 and the second lens L2 to the air gap between the second lens L2 and the third lens L3. This ensures that the three lenses have sufficient space to deflect light, suppressing aberrations. It also provides ample space for assembly of the three lenses and helps to compress the overall length of the endoscope optical system 100, achieving a small-size design.

[0089] In some embodiments, the endoscope optical system 100 satisfies the condition: 2ω ≥ 130°. Here, 2ω is the maximum field of view of the endoscope optical system. When the above condition is satisfied, the endoscope optical system 100 can achieve wide-angle characteristics, meeting the need for a large-area imaging capability of the endoscope.

[0090] It should be noted that, in some embodiments, when the endoscope optical system 100 is applied to the objective lens module, the endoscope optical system 100 can be matched with a photosensitive element having a rectangular photosensitive surface, and the imaging surface 110 of the endoscope optical system 100 can coincide with the photosensitive surface of the photosensitive element. The effective pixel area on the imaging surface 110 can have both horizontal and diagonal directions, and 2ω can be understood as the maximum field of view of the endoscope optical system 100 in the diagonal direction. It can be understood that, in this application, the imaging surface 110 can be understood as a virtual surface formed by the convergence point of the light rays of the endoscope optical system on the image side of the fourth lens L4, and when the endoscope optical system 100 is matched with the photosensitive element, the imaging surface 110 coincides with the photosensitive surface of the photosensitive element, so that the light rays adjusted by the endoscope optical system 100 can form a clear image on the photosensitive surface.

[0091] In some embodiments, the object side of the first lens L1 is a plane, which is beneficial for the assembly and positioning of the endoscope optical system 100 in the endoscope and improves the assembly accuracy.

[0092] Based on the descriptions of the above embodiments, more specific embodiments and accompanying drawings are provided below for detailed explanation.

[0093] First Embodiment

[0094] Please see again. Figure 1 , Figure 1This is a schematic diagram of the endoscope optical system 100 in the first embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0095] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0096] The object side of the first lens L1 is a plane, and the image side is concave near the optical axis.

[0097] The object side of the second lens L2 is convex near the optical axis, and the image side is also convex near the optical axis.

[0098] The object side of the third lens L3 is convex near the optical axis, and the image side is also convex near the optical axis.

[0099] The object side of the fourth lens L4 is concave near the optical axis, and the image side is convex near the optical axis.

[0100] Table 1 below shows detailed parameters of each lens in the endoscopic optical system of the first embodiment, including radius of curvature (at the optical axis), thickness, refractive index, Abbe number, focal length, effective focal length f, maximum field of view 2ω, and aperture number FNO. The reference wavelength for the focal length, refractive index, and Abbe number of each lens, as well as the focal length of the endoscopic optical system 100, is 587.6 nm, which is the same in other embodiments. The elements from the object plane (not shown) to the imaging plane 110 are arranged sequentially from top to bottom according to Table 1. The first row of the first lens L1 represents the object-side surface of the first lens L1, the second row represents the image-side surface of the first lens L1, and so on. The first value in the "thickness" parameter column of the first lens L1 is the thickness of the first lens L1 along the optical axis, and the second value is the distance from the image-side surface of the first lens L1 to the rear surface in the image-side direction (the object-side surface of the second lens L2) along the optical axis 110. The meanings of the other values ​​in the thickness parameter column can be deduced from this.

[0101] It should be noted that in the first embodiment and the following embodiments, the endoscope optical system 100 may also be without the filter 140 and the protective glass 130, but the distance on the optical axis from the image side of the fourth lens L4 to the imaging surface 110 remains unchanged.

[0102] Table 1

[0103]

[0104]

[0105] In the first embodiment, the aspherical coefficients of the object-side or image-side surfaces of each lens in the endoscope optical system 100 are given in Table 2. The surface numbers, from S2 to S4, represent the image-side surface of the first lens L1; S3 and S4 represent the object-side and image-side surfaces of the second lens L2, respectively; S5 and S6 represent the object-side and image-side surfaces of the third lens L3, respectively; and S7 and S8 represent the object-side and image-side surfaces of the fourth lens L4, respectively. The numbers K-A14, from top to bottom, represent the type of aspherical coefficient, where K represents the conic coefficient, A4 represents the fourth-order aspherical coefficient, A6 represents the sixth-order aspherical coefficient, A8 represents the eighth-order aspherical coefficient, and so on.

[0106] In addition, the formula for the aspheric coefficient is as follows:

[0107]

[0108] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the distance from the corresponding point on the aspherical surface to the optical axis, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, and Ai is the coefficient corresponding to the i-th higher-order term in the aspherical surface shape formula.

[0109] Table 2

[0110]

[0111] Please see Figure 2a , Figure 2b and Figure 2c , Figure 2a This is an astigmatism curve of the endoscope optical system 100 in the first embodiment. The horizontal axis represents the focal shift, and the unit is millimeters. Figure 2b This is a distortion curve of the endoscope optical system 100 in the first embodiment. The horizontal axis represents the distortion value, and the unit is percentage. Figure 2c This is a magnification chromatic aberration curve of the endoscope optical system 100 in the first embodiment, with the horizontal axis in μm. Figure 2a , Figure 2b and Figure 2c It can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image deformation caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0112] Second Embodiment

[0113] Please see Figure 3 , Figure 3This is a schematic diagram of the endoscope optical system 100 in the second embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0114] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0115] The object side of the first lens L1 is flat, and the image side is concave near the optical axis.

[0116] The object side of the second lens L2 is convex near the optical axis, and the image side is also convex near the optical axis.

[0117] The object side of the third lens L3 is concave near the optical axis, and the image side is convex near the optical axis.

[0118] The object side of the fourth lens L4 is concave near the optical axis, and the image side is convex near the optical axis.

[0119] In the second embodiment, the parameters of the endoscope optical system 100 are given in Table 3. The definitions of each parameter can be derived from the first embodiment and will not be repeated here.

[0120] Table 3

[0121]

[0122] In the second embodiment, the aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 are given in Table 4, and the definitions of each parameter can be derived from the first embodiment.

[0123] Table 4

[0124]

[0125] Please see Figure 4a , Figure 4b and Figure 4c , Figure 4a This is an astigmatism curve of the endoscope optical system 100 in the second embodiment. Figure 4b This is a distortion curve of the endoscope optical system 100 in the second embodiment. Figure 4c This is a magnification chromatic aberration curve of the endoscope optical system 100 in the second embodiment. Figure 4a , Figure 4b and Figure 4cIt can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image deformation caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0126] Third Embodiment

[0127] Please see Figure 5 , Figure 5 This is a schematic diagram of the endoscope optical system 100 in the third embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0128] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0129] The object side of the first lens L1 is a plane, and the image side is concave near the optical axis.

[0130] The object side of the second lens L2 is convex near the optical axis, and the image side is concave near the optical axis.

[0131] The object side of the third lens L3 is convex near the optical axis, and the image side is also convex near the optical axis.

[0132] The object side of the fourth lens L4 is concave near the optical axis, and the image side is convex near the optical axis.

[0133] In the third embodiment, the parameters of the endoscope optical system 100 are given in Table 5. The definitions of each parameter can be derived from the first embodiment and will not be repeated here.

[0134] Table 5

[0135]

[0136] In the third embodiment, the aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 are given in Table 6, and the definitions of each parameter can be derived from the first embodiment.

[0137] Table 6

[0138]

[0139]

[0140] Please see Figure 6a , Figure 6b and Figure 6c , Figure 6a This is an astigmatism curve of the endoscope optical system 100 in the third embodiment. The horizontal axis represents the focal point offset, and the unit is μm. Figure 6b This is a distortion curve of the endoscope optical system 100 in the third embodiment. Figure 6c This is a magnification chromatic aberration curve of the endoscope optical system 100 in the third embodiment. Figure 6a , Figure 6b and Figure 6c It can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image deformation caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0141] Fourth embodiment

[0142] Please see Figure 7 , Figure 7 This is a schematic diagram of the endoscope optical system 100 in the fourth embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0143] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0144] The object side of the first lens L1 is a plane, and the image side is concave near the optical axis.

[0145] The object side of the second lens L2 is convex near the optical axis, and the image side is also convex near the optical axis.

[0146] The object side of the third lens L3 is convex near the optical axis, and the image side is also convex near the optical axis.

[0147] The object side of the fourth lens L4 is concave near the optical axis, and the image side is convex near the optical axis.

[0148] The parameters of the endoscope optical system 100 in the fourth embodiment are given in Table 7. The definitions of each parameter can be derived from the first embodiment and will not be repeated here.

[0149] Table 7

[0150]

[0151] In the fourth embodiment, the aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 are given in Table 8, and the definitions of each parameter can be derived from the first embodiment.

[0152] Table 8

[0153]

[0154] Please see Figure 8a , Figure 8b and Figure 8c , Figure 8a This is an astigmatism curve of the endoscope optical system 100 in the fourth embodiment. Figure 8b This is a distortion curve diagram of the endoscope optical system 100 in the fourth embodiment. Figure 8c This is a magnification chromatic aberration curve of the endoscope optical system 100 in the fourth embodiment. Figure 8a , Figure 8b and Figure 8c It can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image distortion caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0155] Fifth embodiment

[0156] Please see Figure 9 , Figure 9 This is a schematic diagram of the endoscope optical system 100 in the fifth embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0157] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0158] The object side of the first lens L1 is flat, and the image side is concave near the optical axis.

[0159] The object side of the second lens L2 is convex near the optical axis, and the image side is concave near the optical axis.

[0160] The object side of the third lens L3 is convex near the optical axis, and the image side is also convex near the optical axis.

[0161] The object side of the fourth lens L4 is concave near the optical axis, and the image side is also concave near the optical axis.

[0162] The parameters of the endoscope optical system 100 in the fifth embodiment are given in Table 9. The definitions of each parameter can be derived from the first embodiment and will not be repeated here.

[0163] Table 9

[0164]

[0165]

[0166] In the fifth embodiment, the aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 are given in Table 10, and the definitions of each parameter can be derived from the first embodiment.

[0167] Table 10

[0168]

[0169] Please see Figure 10a , Figure 10b and Figure 10c , Figure 10a This is an astigmatism curve of the endoscope optical system 100 in the fifth embodiment. Figure 10b This is a distortion curve diagram of the endoscope optical system 100 in the fifth embodiment. Figure 10c This is a magnification chromatic aberration curve of the endoscope optical system 100 in the fifth embodiment. Figure 10a , Figure 10b and Figure 10c It can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image distortion caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0170] Sixth Embodiment

[0171] Please see Figure 11 , Figure 11 This is a schematic diagram of the endoscope optical system 100 in the sixth embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0172] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0173] The object side of the first lens L1 is flat, and the image side is concave near the optical axis.

[0174] The object side of the second lens L2 is convex near the optical axis, and the image side is concave near the optical axis.

[0175] The object side of the third lens L3 is convex near the optical axis, and the image side is also convex near the optical axis.

[0176] The object side of the fourth lens L4 is concave near the optical axis, and the image side is convex near the optical axis.

[0177] The parameters of the endoscope optical system 100 in the sixth embodiment are given in Table 11. The definitions of each parameter can be derived from the first embodiment and will not be repeated here.

[0178] Table 11

[0179]

[0180] In the sixth embodiment, the aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 are given in Table 12, and the definitions of each parameter can be derived from the first embodiment.

[0181] Table 12

[0182]

[0183]

[0184] Please see Figure 12a , Figure 12b and Figure 12c , Figure 12a This is an astigmatism curve of the endoscope optical system 100 in the sixth embodiment. Figure 12b This is a distortion curve diagram of the endoscope optical system 100 in the sixth embodiment. Figure 12c This is a magnification chromatic aberration curve of the endoscope optical system 100 in the sixth embodiment. Figure 12a , Figure 12b and Figure 12c It can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image deformation caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0185] Seventh Embodiment

[0186] Please see Figure 13 , Figure 13 This is a schematic diagram of the endoscope optical system 100 in the seventh embodiment. The endoscope optical system 100 includes, from the object side to the image side, a first lens L1 with negative optical power, a second lens L2 with positive optical power, an aperture stop 120, a third lens L3 with positive optical power, a fourth lens L4 with negative optical power, a filter 140, and a protective glass 130.

[0187] The image-side surface of the first lens L1, as well as the object-side surface and image-side surface of the second lens L2, the third lens L3, and the fourth lens L4, are all aspherical.

[0188] The object side of the first lens L1 is flat, and the image side is concave near the optical axis.

[0189] The object side of the second lens L2 is convex near the optical axis, and the image side is concave near the optical axis.

[0190] The object side of the third lens L3 is convex near the optical axis, and the image side is also convex near the optical axis.

[0191] The object side of the fourth lens L4 is concave near the optical axis, and the image side is convex near the optical axis.

[0192] The parameters of the endoscope optical system 100 in the seventh embodiment are given in Table 13. The definitions of each parameter can be derived from the first embodiment and will not be repeated here.

[0193] Table 13

[0194]

[0195] In the seventh embodiment, the aspherical coefficients of the object side or image side of each lens of the endoscope optical system 100 are given in Table 14, and the definitions of each parameter can be derived from the first embodiment.

[0196] Table 14

[0197]

[0198]

[0199] Please see Figure 14a , Figure 14b and Figure 14c , Figure 14a This is an astigmatism curve of the endoscope optical system 100 in the seventh embodiment. Figure 14b This is a distortion curve diagram of the endoscope optical system 100 in the seventh embodiment. Figure 14cThis is a magnification chromatic aberration curve of the endoscope optical system 100 in the seventh embodiment. Figure 14a , Figure 14b and Figure 14c It can be seen that the sagittal and meridional field curvatures of the endoscope optical system 100 are both small, the field curvature and astigmatism of each field of view are well corrected, the center and edge of the field of view have clear imaging, the distortion of the endoscope optical system 100 across the entire field of view is small, the image deformation caused by the main beam is small, the imaging quality of the system is excellent, the magnification chromatic aberration of the endoscope optical system 100 is well corrected, and it has good imaging quality.

[0200] In addition, the endoscope optical system 100 in the first to seventh embodiments satisfies the data in Table 15 below. The meaning of each parameter and the effect that can be obtained by satisfying the data can be referred to the above description.

[0201] Table 15

[0202]

[0203] This application also provides an objective lens module (not shown in the figure), including a photosensitive element and the endoscope optical system 100 described in any of the above embodiments. The photosensitive surface of the photosensitive element can be regarded as the imaging surface 110 of the endoscope optical system 100. Specifically, the photosensitive element can be a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor sensor (CMOS sensor). By using the above-described endoscope optical system 100 in the objective lens module, it is possible to achieve a small size design, wide-angle characteristics, and high imaging quality, thereby facilitating the application of the objective lens module in endoscopes.

[0204] This application also provides an endoscope (not shown), including a housing and an objective lens module as described in any of the above embodiments. The objective lens module is disposed within the housing, which can be the tube of the endoscope objective lens. The endoscope can be applied in the medical field, such as for medical diagnosis of patients. Specifically, the endoscope includes, but is not limited to, endoscopes used to observe digestive organs, bronchi, nasal cavity, pharynx, urinary organs, and uterus. The endoscope can be a flexible endoscope. By using the aforementioned endoscope objective lens in the endoscope, the endoscope objective lens can achieve a small size design, wide-angle characteristics, and high imaging quality. This allows the endoscope to minimize damage to patients when applied in the medical field, acquire images of lesion areas over a wide area to avoid missed diagnoses, and form high-resolution lesion images, improving diagnostic accuracy.

[0205] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0206] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An endoscope optical system, characterized in that, The endoscopic optical system comprises four lenses with optical power, and the endoscopic optical system includes, along the optical axis from the object side to the image side, the following: A first lens with negative optical power, wherein the image-side surface of the first lens is concave near the optical axis; A second lens with positive optical power, wherein the object side of the second lens is convex near the optical axis; A third lens with positive optical power, wherein the image-side surface of the third lens is convex near the optical axis; A fourth lens with negative optical power, wherein the object side of the fourth lens is concave near the optical axis; Furthermore, the endoscopic optical system satisfies the following condition: 4.08≤TTL / f≤4.52; -3≤f2 / f1≤-1.5; Wherein, TTL is the distance on the optical axis from the object side of the first lens to the imaging surface of the endoscope optical system, f is the focal length of the endoscope optical system, f2 is the focal length of the second lens, and f1 is the focal length of the first lens.

2. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: -0.9≤f1 / f≤-0.

7.

3. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: -9.9≤f4 / f3≤-1.7; Where f4 is the focal length of the fourth lens and f3 is the focal length of the third lens.

4. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: 1.45≤Bf / f≤1.72; Wherein, Bf is the distance on the optical axis from the image side of the fourth lens to the imaging surface of the endoscope optical system.

5. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: 1.6≤f2 / f≤2.

4.

6. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: 0.7 ≤ f3 / f ≤ 1.4; Where f3 is the focal length of the third lens.

7. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: 1.51mm -1 ≤FNO / TTL≤1.7mm -1 ; Wherein, FNO is the aperture number of the endoscope optical system.

8. The endoscopic optical system according to claim 1, characterized in that, The endoscope optical system satisfies the following condition: 0.05≤|R7 / R8|≤0.77; where R7 is the radius of curvature of the object-side surface of the fourth lens at the optical axis, and R8 is the radius of curvature of the image-side surface of the fourth lens at the optical axis; and / or, 0.02≤|R4 / R5|≤1.44; where R4 is the radius of curvature of the image side of the second lens at the optical axis, and R5 is the radius of curvature of the object side of the third lens at the optical axis.

9. An objective lens module, characterized in that, It includes a photosensitive element and an endoscope optical system as described in any one of claims 1-8, wherein the photosensitive element is disposed on the image side of the endoscope optical system.

10. An endoscope, characterized in that, Includes the objective lens module as described in claim 9.

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