Objective lens for an endoscope and endoscope

Abstract

The application discloses an objective lens of an endoscope and the endoscope. The objective lens comprises a flat optical element and a first lens arranged in sequence along an optical axis from an object side to an image side. The first lens is a glass lens. The first lens has a negative optical power. The object side of the first lens is an aspheric surface. The object side of the first lens comprises a central surface in a central region and an annular surface surrounding the central surface. The central surface is a concave surface. The absolute value of the tangential angle of the annular surface at each position is less than or equal to 0.1°. At least a part of the annular surface is located in an effective light passing region. The image side of the flat optical element is attached to the annular surface through an attachment layer. The objective lens of the endoscope and the endoscope provided by the application can simultaneously meet the requirements of a large field angle, low optical distortion, reliable waterproof sealing, high temperature sterilization resistance and good manufacturability. The technical contradiction between distortion correction and waterproof gluing of the existing aspheric endoscope objective lens is solved.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and more particularly to an objective lens for an endoscope and an endoscope. Background Technology

[0002] Endoscope objectives need to be waterproof, and wide-field-of-view endoscopes require the use of aspherical surfaces to reduce distortion. With the adoption of aspherical surfaces, the waterproofing process for endoscopes designed for spherical systems needs corresponding adjustments. To improve waterproofing performance, the shape of the aspherical surface needs to be specially designed.

[0003] Endoscopic objectives need to simultaneously meet the requirements of wide field of view observation and reliable waterproofing, and using aspherical lenses is a key means to reduce distortion in a wide field of view.

[0004] In related solutions, a plastic aspherical lens adjacent to the protective window is used to correct aberrations. To utilize the mature and low-cost adhesive waterproofing process, one design approach is to make the object-side surface of the aspherical lens planar and the image-side surface aspherical, allowing for bonding and sealing with the protective window via the planar surface, similar to a plano-concave lens in a conventional spherical system. However, because off-axis beams intersect on the image-side surface of the lens, aberration correction is difficult, hindering effective distortion control. Another approach designs the object-side surface of the aspherical lens as convex, which facilitates molding, but the convex shape causes the lens edge to be far from the protective window, increasing the front window size and preventing bonding, resulting in poor waterproofing reliability.

[0005] Therefore, when the object side of the first lens is designed as an aspherical surface to correct large field-of-view distortion, the aspherical shape makes it difficult to meet the requirements of reliable waterproof bonding. This results in the inability to provide a waterproof adhesive layer with sufficient bonding area between the protective window and the aspherical lens while achieving low distortion, thus limiting the overall waterproof performance of the objective lens. Summary of the Invention

[0006] This invention provides an objective lens for an endoscope and an endoscope in order to solve the technical problem that aspherical objective lenses cannot simultaneously achieve a large field of view, low distortion, and reliable waterproof performance.

[0007] According to one aspect of the present invention, an objective lens for an endoscope is provided, comprising a flat optical element and a first lens arranged sequentially along the optical axis from the object side to the image side; The first lens is a glass lens, the first lens has negative optical power, and the object side of the first lens is aspherical; The object-side surface of the first lens includes a central surface located in the central region and an annular surface surrounding the central surface. The central surface is concave, and the absolute value of the tangential angle of the annular surface at each position is less than or equal to 0.1°. Wherein, the tangential angle is the angle between the tangent plane at any position within the annular surface and the plane perpendicular to the optical axis; At least a portion of the annular surface is located in the effective light-transmitting area; The image-side surface of the flat optical element is bonded to the annular surface via an adhesive layer.

[0008] Optionally, the absolute value of the difference between the largest and smallest tangential angles at each location of the annular surface is less than or equal to 0.1°.

[0009] Optionally, the inner radius of the annular surface is greater than or equal to 85% of the maximum field-of-view beam aperture on the object side of the first lens.

[0010] Optionally, the radial width of the annular surface is greater than or equal to 37.8% of the effective half-aperture of the object side of the first lens.

[0011] Optionally, the thickness of the bonding layer is less than or equal to 0.01 mm.

[0012] Optionally, the field of view of the objective lens is greater than or equal to 70°.

[0013] Optionally, the objective lens may further include a lens group located on the image side of the first lens; The lens group includes a second lens, a third lens, and a fourth lens arranged sequentially from the object side to the image side along the optical axis; The second lens has positive optical power, the third lens has negative optical power, and the fourth lens has positive optical power.

[0014] Optionally, the third lens and the fourth lens constitute a first cemented lens.

[0015] Optionally, the objective lens may also include optical elements with no optical power; The optical element is located in the optical path between the first lens and the second lens.

[0016] According to another aspect of the invention, an endoscope is provided, comprising the objective lens of any of the endoscopes described in the first aspect.

[0017] The endoscope objective and endoscope provided in this embodiment of the invention feature a concave central surface and an approximately planar annular surface surrounding the central surface on the object-side surface of the first lens. The absolute value of the tangential angle θ at each position on the annular surface is controlled to be less than or equal to 0.1°, allowing the image-side surface of the flat optical element to reliably bond with the annular surface through an adhesive layer. Simultaneously, the first lens is made of glass, capable of withstanding harsh sterilization conditions such as high-temperature, high-pressure water vapor and ethylene oxide immersion. Furthermore, the approximately planar design of the annular surface avoids excessive curvature, meeting the feasibility requirements of glass molding processes. The concave aspherical design of the central surface effectively corrects optical distortion under large field of view, significantly reducing distortion from approximately 20% to below 2%. The approximately planar design of the annular surface provides an ideal operating interface for the waterproofing process, increasing the effective thickness of the waterproofing adhesive from only equal to the thickness of the flat optical element itself to the radial width of the annular surface, thus significantly enhancing waterproofing reliability. This achieves a balance between a large field of view, low optical distortion, reliable waterproof sealing, high-temperature sterilization resistance, and good manufacturability, resolving the technical contradiction that existing aspherical endoscope objectives cannot simultaneously achieve distortion correction and cemented waterproofing.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of an objective lens of an endoscope provided in an embodiment of the present invention; Figure 2 for Figure 1 A magnified schematic diagram of the medium-sized flat-panel optical element and the first lens; Figure 3 A schematic diagram of the objective lens of another endoscope provided in an embodiment of the present invention; Figure 4 for Figure 3 A magnified schematic diagram of the medium-sized flat-panel optical element and the first lens; Figure 5 A schematic diagram of the objective lens of another endoscope provided in an embodiment of the present invention; Figure 6 for Figure 5A magnified schematic diagram of the medium-sized flat-panel optical element and the first lens; Figure 7 A schematic diagram of the objective lens of another endoscope provided in an embodiment of the present invention; Figure 8 for Figure 7 A magnified schematic diagram of the medium-sized flat-panel optical element and the first lens; Figure 9 This is a schematic diagram of the structure of a first lens provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of the object-side surface of a first lens provided in an embodiment of the present invention; Figure 11 This is a schematic diagram of the optical path at the front end of an objective lens provided in an embodiment of the present invention; Figure 12 This is a schematic diagram of optical distortion of an endoscope objective lens provided in an embodiment of the present invention; Figure 13 A grid distortion diagram of an endoscope objective lens provided in an embodiment of the present invention; Figure 14 A schematic diagram of optical distortion of the objective lens of another endoscope provided in an embodiment of the present invention; Figure 15 A grid distortion diagram of the objective lens of another endoscope provided in an embodiment of the present invention; Figure 16 This is a schematic diagram of a structure for bonding a flat optical element to a first lens according to an embodiment of the present invention; Figure 17 This is a schematic diagram of a planar optical element and a first lens not being bonded together, according to an embodiment of the present invention. Figure 18 This is a schematic diagram of the optical path of a flat optical element and a first lens provided in an embodiment of the present invention; Figure 19 This is a schematic diagram of the optical path of another flat optical element and a first lens provided in an embodiment of the present invention; Figure 20 This is a schematic diagram of the optical path of another flat optical element and a first lens provided in an embodiment of the present invention; Figure 21 This is a schematic diagram of the structure of a flat optical element and a first lens provided in an embodiment of the present invention; Figure 22 This is a schematic diagram of the optical path of another flat optical element and a first lens provided in an embodiment of the present invention; Figure 23 An MTF curve of an objective lens provided in an embodiment of the present invention; Figure 24 MTF curve of another objective lens provided in an embodiment of the present invention; Figure 25 MTF curve of another objective lens provided in an embodiment of the present invention; Figure 26 This is a schematic diagram of another planar optical element and a first lens provided in an embodiment of the present invention; Figure 27 MTF curve of the objective lens of the endoscope provided in Embodiment 1 of the present invention when the flat optical element and the first lens are not attached; Figure 28 The MTF curve of the objective lens of the endoscope provided in Embodiment 1 of the present invention after the flat optical element and the first lens are bonded together; Figure 29 This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 1 of the present invention; Figure 30 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 2 of the present invention when the flat optical element and the first lens are not attached. Figure 31 The MTF curve of the objective lens of the endoscope provided in Embodiment 2 of the present invention after the flat optical element and the first lens are bonded together; Figure 32 This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 2 of the present invention; Figure 33 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 3 of the present invention when the flat optical element and the first lens are not attached. Figure 34 The MTF curve of the objective lens of the endoscope provided in Embodiment 3 of the present invention after the flat optical element and the first lens are bonded together; Figure 35 This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 3 of the present invention; Figure 36 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 4 of the present invention when the flat optical element and the first lens are not attached. Figure 37 The MTF curve of the objective lens of the endoscope provided in Embodiment 4 of the present invention after the flat optical element and the first lens are bonded together; Figure 38 This is a field distortion diagram of the objective lens of the endoscope provided in Embodiment 4 of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0023] Figure 1 This is a schematic diagram of the structure of an objective lens of an endoscope provided in an embodiment of the present invention. Figure 2 for Figure 1 A magnified schematic diagram of the medium-plate optical element and the first lens. Figure 3 This is a schematic diagram of the objective lens of another endoscope provided in an embodiment of the present invention. Figure 4 for Figure 3 A magnified schematic diagram of the medium-plate optical element and the first lens. Figure 5 This is a schematic diagram of the structure of an objective lens of another endoscope provided in an embodiment of the present invention. Figure 6 for Figure 5 A magnified schematic diagram of the medium-plate optical element and the first lens. Figure 7 This is a schematic diagram of the objective lens of another endoscope provided in an embodiment of the present invention. Figure 8 for Figure 7 A magnified schematic diagram of the medium-plate optical element and the first lens. Figure 9 This is a schematic diagram of the structure of a first lens provided in an embodiment of the present invention. Figure 10 This is a schematic diagram of the object-side surface of a first lens provided in an embodiment of the present invention, as shown below. Figures 1-10As shown, the objective lens of the endoscope provided in this embodiment of the invention includes a flat optical element L0 and a first lens L1 arranged sequentially along the optical axis from the object side to the image side. The first lens L1 is a glass lens with negative optical power, and its object-side surface is aspherical. The object-side surface of the first lens L1 includes a central surface 10 located in the central region and an annular surface 11 surrounding the central surface 10. The central surface 10 is concave, and the absolute value of the tangential angle θ at each position of the annular surface 11 is less than or equal to 0.1°. The tangential angle θ is the angle between the tangent surface at any position within the annular surface 11 and a plane perpendicular to the optical axis. At least a portion of the annular surface 11 is located in the effective light-transmitting region 100, and the image-side surface of the flat optical element L0 is bonded to the annular surface 11 through an adhesive layer 20.

[0024] In the objective lens of the endoscope provided in this embodiment, each lens can be fixed to a metal tube ( Figure 1 (Not shown in the image). The metal lens tube provides support and protection for each optical element, ensuring their precise alignment along the optical axis and maintaining stable relative positions. The flat optical element L0 is typically fixed to the front end of the metal lens tube, serving as the entrance window for the objective lens, and is sealed to the metal lens tube by adhesive application or welding. The first lens L1 and subsequent lens groups are sequentially assembled inside the metal lens tube. It should be noted that fixing each lens to the metal lens tube is only an exemplary assembly method; those skilled in the art can employ other suitable support structures or fixing methods according to actual application requirements.

[0025] Among them, the flat optical element L0 refers to an optical element whose object side and image side are both flat, with zero optical power. It is mainly used to protect the internal optical elements and serve as a physical barrier at the front of the objective lens.

[0026] It should be noted that medical endoscopes require strict sterilization procedures during use, commonly including high-temperature, high-pressure steam sterilization, ethylene oxide immersion, and hydrogen peroxide plasma sterilization. Therefore, the endoscope body must have a reliable waterproof structure, especially the objective lens at the tip, which is highly susceptible to liquid intrusion during sterilization.

[0027] In some embodiments, the flat optical element L0 is a sapphire window. Sapphire material has high hardness, scratch resistance, and excellent chemical stability, and can withstand the harsh conditions of high temperature and high pressure water vapor, ethylene oxide immersion, and hydrogen peroxide plasma during the endoscope sterilization process.

[0028] Furthermore, there are two important requirements for the clinical application of endoscopes: on the one hand, in order to reduce the patient's wound, the mechanical size of the endoscope tube needs to be as small as possible; on the other hand, in order to expand the doctor's observation range and reduce the omission of lesions, the objective lens needs to have a large optical field of view.

[0029] However, Figure 11 This is a schematic diagram of the optical path of an objective lens front end provided in an embodiment of the present invention, as shown below. Figure 11 As shown, the red light corresponds to a field of view of 70 degrees, and the green light corresponds to a field of view of 60 degrees. The incident height of the red light on the flat optical element L0 is significantly greater than that of the green light; therefore, the flat optical element L0 required for the red light is larger than that for the green light. This demonstrates that as the field of view increases, the incident height of the peripheral rays on the flat optical element L0 at the front of the objective lens also increases, forcing a corresponding increase in the radial dimension of the flat optical element L0. This, in turn, leads to a thicker outer diameter of the metal tube encasing the flat optical element L0, which is detrimental to meeting the requirements for a smaller diameter.

[0030] In this embodiment of the invention, the first lens L1 is located after the flat optical element L0 and is used to converge angularly incident light rays so that subsequent lens groups can continue to transmit and image. Specifically, the first lens L1 is configured as a negative lens to enable it to diverge light rays, thereby converging light rays incident over a large field of view. By effectively converging off-axis light rays through the first lens L1, the incident height of light rays at the edge of the large field of view on subsequent optical elements can be reduced. This facilitates optical transmission over a large field of view within a compact radial space and alleviates the conflict between a large field of view and a smaller lens tube diameter.

[0031] At the same time, the expansion of the field of view also leads to a significant increase in optical distortion.

[0032] For example, Figure 12 This is a schematic diagram of the optical distortion of an endoscope objective lens provided in an embodiment of the present invention. Figure 13 A grid distortion diagram of an endoscope objective lens provided in an embodiment of the present invention, such as... Figure 12 and Figure 13 As shown, for a conventional 70-degree field-of-view endoscope, the absolute value of its full-field optical distortion is usually as high as about 20%, and the resulting image distortion will affect the doctor's accurate observation and judgment of the size and shape of the lesion.

[0033] In order to correct distortion under a large field of view, in this embodiment, the first lens L1 immediately following the flat optical element L0 is designed as an aspherical lens.

[0034] Figure 14 This is a schematic diagram of the optical distortion of the objective lens of another endoscope provided in an embodiment of the present invention. Figure 15 A grid distortion diagram of the objective lens of another endoscope provided in an embodiment of the present invention, such as... Figure 14 and Figure 15As shown, by designing the first lens L1 as an aspherical lens, the aberration correction capability of the aspherical surface can be used to significantly reduce the distortion from about 20% to less than 2%, thereby significantly improving the grid distortion and restoring the true morphology of the lesion.

[0035] Furthermore, in some embodiments, the flat optical element L0 at the tip of the endoscope is welded to the metal tube to achieve waterproofing of the objective lens. While welding offers high airtightness and reliability, it is relatively expensive.

[0036] In this embodiment of the invention, the flat optical element L0 and the first lens L1 are glued together to achieve waterproofing of the objective lens end. The glue process is a mature and inexpensive technology.

[0037] In some embodiments where the first lens L1 is a spherical lens, the first lens L1 may be a plano-concave lens (the object side is a plane and the image side is a concave surface). With this configuration, the object side (plane) of the plano-concave lens can be directly bonded to the flat optical element L0.

[0038] Figure 16 This is a schematic diagram of a structure for bonding a flat optical element to a first lens according to an embodiment of the present invention. Figure 17 This is a schematic diagram of a planar optical element and a first lens not being bonded together, as provided in an embodiment of the present invention. Figure 17 As shown, the flat optical element L0 and the first lens L1 are supported by a spacer 41 in the metal lens tube 40. The spacer 41 provides a predetermined axial distance between the flat optical element L0 and the first lens L1, and a gap 42 is formed between the image-side surface of the flat optical element L0 and the object-side surface of the first lens L1. During the sterilization process, the sterilizing gas or liquid 50 may penetrate along the interface between the flat optical element L0 and the metal lens tube 40 and enter the gap 42, which can easily cause corrosion or damage to the optical elements inside the objective lens, resulting in a decrease in the image quality of the objective lens.

[0039] And such Figure 16 As shown, after the flat optical element L0 is bonded to the first lens L1, the space between them is completely filled with adhesive, preventing the gas or liquid 50 used for disinfection from penetrating the gap, thus achieving a reliable waterproof seal. Simultaneously, bonding allows the edges of the flat optical element L0 and the first lens L1 to be as close as possible, thereby reducing the size of the flat optical element L0.

[0040] Figure 18 This is a schematic diagram of the optical path of a flat optical element and a first lens provided in an embodiment of the present invention. Figure 19 This is a schematic diagram of the optical path of another flat optical element and a first lens provided in an embodiment of the present invention. Figure 18The medium-sized optical element L0 is located close to the first lens L1. Figure 19 There is a large gap between the medium-sized flat optical element L0 and the first lens L1.

[0041] Among them, such as Figure 18 As shown, the flat optical element L0 is closely fitted to the edge of the first lens L1, allowing off-axis rays to pass through within a small radial dimension. In this case, the diameter of the flat optical element L0 can be designed to be relatively small; while Figure 19 Because the distance between the flat optical element L0 and the first lens L1 is relatively large, the incident height of off-axis rays when they reach the flat optical element L0 is significantly increased, forcing the diameter of the flat optical element L0 to increase accordingly. Therefore, by arranging the flat optical element L0 and the first lens L1 close to each other at their edges, the radial dimension of the front-end flat optical element L0 can be effectively reduced, which is beneficial for the design of a smaller diameter endoscope tube.

[0042] As mentioned above, the first lens L1 is set as a plano-concave aspherical lens, that is, the side of the first lens L1 adjacent to the flat optical element L0 (i.e., the object side) is set as a plane, and the aberration is corrected only by the aspherical coefficient of the other side (i.e., the image side). The plane is directly bonded to the flat optical element L0 to achieve a waterproof sealing effect.

[0043] However, Figure 20 This is a schematic diagram of the optical path of another planar optical element and a first lens provided in an embodiment of the present invention, as shown below. Figure 20 As shown, the inventors discovered through research that off-axis beams (such as...) Figure 20 When the red and green beams (in the image) pass through the object side of the first lens L1, the light rays from different fields of view are largely separated from each other. This provides favorable conditions for independently correcting aberrations, especially distortions, in different off-axis fields of view. However, when the off-axis beam passes through the image side, the light rays from different fields of view intersect with each other, making it difficult to perform targeted and independent aberration correction for each field of view.

[0044] Therefore, in order to effectively correct large field-of-view distortion, in this embodiment of the invention, the object-side surface of the first lens L1 is designed as an aspherical surface.

[0045] In some embodiments, the object side of the first lens L1 is designed to be convex. With this configuration, its surface shape can be directly molded without the need for a core extraction process, which has an advantage in manufacturing cost.

[0046] However, further research by the inventors revealed that the convex aspherical surface has limited distortion correction capabilities, with the absolute distortion value only reduced to approximately 10%, failing to meet the requirement for lower distortion. Simultaneously, the convex shape of the aspherical surface causes the edge of the first lens L1 to be far from the flat optical element L0, preventing a tight fit. Furthermore, the increased edge distance leads to a corresponding increase in the necessary dimensions of the flat optical element L0, hindering the reduction of the lens tube diameter. Additionally, the flat optical element L0 cannot be glued to the convex aspherical first lens L1; in this case, the effective waterproof thickness of the adhesive is only equal to the thickness of the flat optical element L0 itself, resulting in a short waterproof sealing path and insufficient reliability. Therefore, a more expensive welding process must be employed to achieve waterproofing.

[0047] In embodiments of the present invention, such as Figure 9 and Figure 10 As shown, the object-side surface of the first lens L1 includes a central surface 10 located in the central region. The central surface 10 refers to the portion of the optical surface of the object-side surface of the first lens L1 located in the central region near the optical axis. The central surface 10 is located in the central region of the object-side surface of the first lens L1, extending outward from the optical axis. It does not cover the entire object-side surface, but rather a part of it.

[0048] Furthermore, the central surface 10 is concave, undertaking the main distortion correction function of the optical system. Since the light rays from different fields of view are significantly separated when the off-axis beam passes through the object side, designing the central surface 10 as a concave aspherical surface is beneficial for independently correcting off-axis aberrations in different fields of view, thereby significantly reducing the optical distortion of the large field-of-view endoscope from the conventional approximately 20% to below 2%.

[0049] like Figure 9 and Figure 10 As shown, the object-side surface of the first lens L1 also includes an annular surface 11 surrounding the central surface 10. The annular surface 11 refers to the ring-shaped portion of the optical surface of the first lens L1 that is arranged around the central surface 10. The annular surface 11 is located in the edge region of the object-side surface of the first lens L1, surrounding and adjacent to the central surface 10. The inner boundary of the annular surface 11 connects to the outer boundary of the central surface 10, and the outer boundary of the annular surface 11 extends to or beyond the edge of the effective light-transmitting area of ​​the object-side surface of the first lens L1.

[0050] Furthermore, such as Figure 9 As shown, for a point A on the annular surface 11, in the cross section passing through the optical axis and point A, draw a tangent to the annular surface 11 through point A, and at the same time draw a straight line perpendicular to the optical axis. The angle between the tangent and the straight line perpendicular to the optical axis is the tangential angle θ at point A.

[0051] In this embodiment of the invention, the absolute value of the tangential angle θ at all positions on the annular surface 11 is controlled within a range of no more than 0.1°, so that the deviation between the surface shape of the annular surface 11 and the ideal plane is extremely small, and it essentially constitutes a high-precision approximate planar region.

[0052] Furthermore, the image-side surface of the flat optical element L0 is bonded to the annular surface 11 through the bonding layer 20.

[0053] The bonding layer 20 can be made of a transparent optical adhesive, such as UV-curable optical adhesive, which is applied to the gap between the annular surface 11 and the image side of the flat optical element L0 by a dispensing process, and then cured by ultraviolet light to form a sealed and waterproof layer.

[0054] During the dispensing and bonding process, because the tangential angle θ at all points on the annular surface 11 is small, the adhesive can flow smoothly within the near-planar area (i.e., the annular surface 11), facilitating the removal of air bubbles and avoiding reduced bonding strength and optical defects caused by residual air bubbles, thus forming a reliable waterproof seal. If external disinfectant liquids or gases are to penetrate the internal cavity formed between the central surface 10 and the flat optical element L0, they must penetrate the entire radial width of the bonding layer 20, resulting in a long waterproof seal path and high reliability.

[0055] Meanwhile, the image side of the flat optical element L0 is a plane, and the annular surface 11 is an approximate plane. The two optical interfaces of the bonding layer 20 formed between the two are basically parallel, so that the bonding layer 20 is equivalent to a flat plate with an optical power close to zero. When the beam of the peripheral field of view passes through this bonding area, it will not introduce significant wavefront error, thus ensuring that the imaging quality of the peripheral area of ​​the image plane will not be significantly degraded due to the adhesive.

[0056] Figure 21 This is a schematic diagram of the structure of a flat optical element and a first lens provided in an embodiment of the present invention, as shown below. Figure 21 As shown, in some embodiments, the first lens L1 is a plastic aspherical lens, with a portion of its edge set as a plane 60. However, this plane 60 is a mechanically truncated surface during the injection molding of the plastic aspherical lens. Its function is to accommodate the injection gate allowance and provide a mechanical support surface, and it does not have a light-transmitting function. This mechanical truncation limits the effective light-transmitting area of ​​the lens, thus restricting the field of view and preventing full utilization of the lens's radial dimensions. For endoscope applications where size is severely limited, this waste of lens size is detrimental to meeting the requirements for smaller diameter lenses, and the plastic material itself cannot withstand high-temperature and high-pressure sterilization.

[0057] Therefore, in this embodiment of the invention, the first lens L1 is a glass lens. The glass material ensures that the lens can withstand harsh sterilization conditions such as high-temperature and high-pressure water vapor and ethylene oxide immersion, avoiding deformation or performance failure of the plastic lens at high temperatures.

[0058] Meanwhile, unlike the mechanically flattened plastic aspherical surfaces that do not have light-transmitting function, in this invention, at least a portion of the annular surface 11 is located within the effective light-transmitting area 100. The effective light-transmitting area 100 refers to the area on the object side of the first lens L1 that actually participates in optical imaging and allows imaging light to pass through.

[0059] The effective light-transmitting area 100 is the region on the object side of the first lens L1 that receives imaging light rays from the object side and ultimately reaches the image plane. The optical surface within this region actually performs the functions of refraction and aberration correction of the imaging light rays. In contrast, the portion outside the effective light-transmitting area, although it may be physically part of the lens, does not participate in optical imaging. Examples include the edge chamfer of the lens, mechanical bearing surfaces, or flattened structures required for injection molding processes.

[0060] It is understandable that the boundary of the effective light-transmitting area 100 is usually determined by the incident range of the maximum field-of-view beam of the optical system on the object side of the first lens L1. With the beam boundary of 100% field of view as the limit, the effective light-transmitting area 100% corresponds to the entire area covered by half the aperture extending from the center of the optical axis to the edge of the 100% field-of-view beam.

[0061] In this embodiment of the invention, at least a portion of the annular surface 11 is located within the effective light-transmitting area 100. The annular surface 11 is not a redundant structure but an effective optical surface that actually participates in optical imaging. Compared to the plane of the edge of the plastic aspherical surface (which is mechanically flattened and not located within the effective light-transmitting area), this embodiment can make full use of the radial dimension of the first lens L1, which is beneficial to achieve optical transmission with a large field of view in a compact space. At the same time, the annular surface 11 (approximately planar area) also undertakes the function of bonding and waterproofing with the flat optical element L0, thus achieving a balance between optical performance and sealing function.

[0062] Furthermore, due to limitations in the molding process, the shape of aspherical glass is subject to many restrictions; for example, it cannot have excessive curvature. However, in this embodiment of the invention, the gentle surface change prevents the annular surface 11 from undergoing excessive curvature changes during the molding process, thus meeting the feasibility requirements of the glass molding process and ensuring the manufacturability of the glass material.

[0063] In summary, the objective lens of the endoscope provided in this embodiment of the invention, by setting a concave central surface in the central region and an approximately planar annular surface surrounding the central surface on the object-side surface of the first lens, and controlling the absolute value of the tangential angle θ at each position of the annular surface to be less than or equal to 0.1°, allows the image-side surface of the flat optical element to be reliably bonded to the annular surface through an adhesive layer. Simultaneously, the first lens is made of glass, capable of withstanding harsh sterilization conditions such as high-temperature, high-pressure water vapor and ethylene oxide immersion, and the approximately planar design of the annular surface avoids excessive curvature, meeting the feasibility requirements of glass molding processes. Specifically, the concave aspherical design of the central surface effectively corrects optical distortion under a large field of view, significantly reducing distortion from approximately 20% to below 2%; the approximately planar design of the annular surface provides an ideal operating interface for the waterproofing process, greatly increasing the effective thickness of the waterproof adhesive from only equal to the thickness of the flat optical element itself to the radial width of the annular surface, significantly enhancing waterproof reliability. This achieves a balance between a large field of view, low optical distortion, reliable waterproof sealing, high-temperature sterilization resistance, and good manufacturability, resolving the technical contradiction that existing aspherical endoscope objectives cannot simultaneously achieve distortion correction and cemented waterproofing.

[0064] As a possible implementation, the absolute value of the difference between the largest and smallest tangential angles at each position of the annular surface 11 is less than or equal to 0.1°.

[0065] Specifically, the absolute value of the tangential angle θ at each point on the annular surface 11 is controlled within a small range, and the fluctuation range of the tangential angle θ on the entire annular surface 11 is also strictly limited to within 0.1°.

[0066] This design ensures that the annular surface 11 has a highly consistent flatness throughout the entire annular region, preventing excessive variations in the tangential angle in local areas that could lead to uneven thickness of the bonding layer 20. Understandably, when the fluctuation of the tangential angle θ is controlled within 0.1°, the gap between the annular surface 11 and the image-side surface of the flat optical element L0 changes minimally. This facilitates uniform filling and smooth expulsion of air bubbles during the dispensing process of the bonding layer 20, thereby ensuring the optical quality of the adhesive interface and the reliability of the waterproof seal.

[0067] As a feasible implementation, the inner radius R1 of the annular surface 11 is greater than or equal to 85% of the maximum field-of-view beam aperture on the object side of the first lens L1.

[0068] Wherein, the inner radius R1 of the annular surface 11 refers to the radial distance from the boundary of the annular surface 11 near the optical axis to the optical axis. In other words, the inner radius R1 of the annular surface 11 is the half-aperture position of the boundary line between the annular surface 11 and the central surface 10, and the radial range of the annular surface 11 extends outward from this boundary line to the edge of the effective light-transmitting area on the object side of the first lens L1.

[0069] The maximum field-of-view beam aperture refers to the radial range covered by a beam covering 100% of the field of view on the object-side surface of the first lens L1 in an optical system. Specifically, the incident height of the marginal rays of the maximum field-of-view beam on the object-side surface of the first lens L1 is the maximum field-of-view beam aperture (half-aperture), and twice that is the aperture itself. The maximum field-of-view beam aperture defines the outer boundary of the effective light-passing area on the object-side surface of the first lens L1.

[0070] Figure 22 This is a schematic diagram of the optical path of another flat optical element and a first lens provided in an embodiment of the present invention. Figure 23 This is an MTF curve of an objective lens provided in an embodiment of the present invention. Figure 24 This is an MTF curve of another objective lens provided in an embodiment of the present invention. Figure 25 Another MTF curve of an objective lens provided in an embodiment of the present invention, such as... Figures 22-25 As shown, further research by the inventors revealed that after the image-side surface of the flat optical element L0 is bonded to the annular surface 11 via the bonding layer 20, both air and adhesive media exist simultaneously in the space between the flat optical element L0 and the first lens L1. At the interface between these two media, image quality deterioration occurs. Therefore, limiting the inner diameter of the annular surface 11 (the approximately planar region) to a minimum can control the location of image quality degradation areas, and the impact on image quality decreases as the approximately planar region approaches its edge.

[0071] Specifically, Figure 23 The corresponding MTF curve when the surrounding light beam passes through both glue and air simultaneously. Figure 24 The corresponding MTF curve when the surrounding beam only passes through air. Figure 25 The MTF curve corresponding to the peripheral light beam passing only through the glue. For example... Figures 23-25 As shown, when the peripheral beam passes through only air or only the adhesive medium, the MTF curve remains good, and the image quality does not deteriorate significantly. However, when a portion of the peripheral beam passes through the adhesive (such as...), the image quality deteriorates. Figure 22 (Medium green beam), part of the beam passes through the air (such as...) Figure 22 When the blue light beam (i.e., the peripheral light beam) passes through both glue and air simultaneously, it may cause a sudden change in the wavefront, resulting in a significant drop in the MTF curve, indicating a significant degradation in image quality.

[0072] Typically, users are more sensitive to image quality in the central area of ​​the image, such as within 85% of the image diameter, and relatively less sensitive to image quality degradation in the outer ring. Therefore, in this embodiment, controlling the inner radius of the annular surface 11 to be no less than the beam boundary of 85% of the field of view, that is, ensuring that the beam within 85% of the field of view only passes through air and not through glue, helps to reduce the probability of image quality degradation entering the user's sensitive internal area, thereby ensuring stable and excellent imaging quality in the main observation area.

[0073] Furthermore, if the inner radius of the annular surface 11 is too small, it will compress the usable area of ​​the central surface 10, causing the aspherical surface to degenerate towards the plane, thus weakening its ability to correct distortion. Therefore, properly setting the starting position of the annular surface 11 to be at least outside the 85% field-of-view beam boundary can reserve sufficient radial space for the central surface 10 to fully utilize its aspherical distortion correction function.

[0074] As a possible implementation, the radial width D1 of the annular surface 11 is greater than or equal to 37.8% of the effective half-aperture of the object side surface of the first lens L1.

[0075] Wherein, the radial width D1 of the annular surface 11 refers to the difference between the outer radius and the inner radius of the annular surface 11. Specifically, the outer radius of the annular surface 11 is the radial distance from the boundary of the annular surface 11 away from the optical axis to the optical axis, and the inner radius of the annular surface 11 is the radial distance from the boundary of the annular surface 11 close to the optical axis to the optical axis. The difference between the two is the width of the annular surface 11 extending radially. This width directly determines the radial bonding length of the bonding layer 20 between the flat optical element L0 and the first lens L1.

[0076] The effective half-aperture refers to the maximum half-aperture corresponding to the light beam covering 100% of the field of view on the object-side surface of the first lens L1 in an optical system. Specifically, the incident height of the marginal ray at the maximum field of view on the object-side surface of the first lens L1 is the effective half-aperture of that object-side surface. The effective half-aperture defines the outer boundary of the effective light-transmitting area 100 on the object-side surface of the first lens L1.

[0077] Figure 26 This is a schematic diagram of another planar optical element and a first lens provided in an embodiment of the present invention, as shown below. Figure 26 As shown, the wider the radial width D1 of the annular surface 11, the greater the radial bonding width t of the adhesive layer 20. The longer the path that external gas or liquid needs to penetrate the adhesive to enter the cavity region 43, the stronger the waterproofing capability.

[0078] Therefore, in this embodiment, by setting the radial width D1 of the annular surface 11 to be no less than 37.8% of the effective half-aperture, sufficient dispensing width can be ensured, and a sufficiently long waterproof sealing path can be constructed within a limited radial space, thereby significantly improving the waterproof reliability of the objective lens under harsh environments such as high temperature and high pressure sterilization.

[0079] In terms of specific design methods, precise control of various parameters of the annular surface 11 can be achieved through control functions provided by optical design software. For example, the SDRV function in Zemax software or the SDERIVF function in CodeV software can be used to precisely control and optimize the magnitude of the tangential angle θ at various positions on the annular surface 11; the REAY function in Zemax software or the MAP function in CodeV software can be used to indirectly control the inner radius and radial width of the annular surface 11 by controlling the incident height of the light rays on the object side.

[0080] It should be noted that Zemax and CodeV are merely examples of commonly used optical design software. Those skilled in the art can also use other optical design software with similar functions to achieve the above design goals, which will not be elaborated here.

[0081] As one possible implementation, the thickness of the bonding layer 20 is less than or equal to 0.01 mm.

[0082] If the adhesive layer of the bonding layer 20 is too thick, a non-negligible optical path difference will be introduced when light passes through the bonding layer 20, resulting in an increase in wavefront error and a decrease in image quality of the surrounding field of view.

[0083] In this embodiment, by controlling the thickness of the bonding layer 20 to within 0.01 mm, the influence of the bonding layer 20 on the imaging beam can be minimized, ensuring that the imaging quality of the peripheral field of view is not significantly degraded due to the dispensing process.

[0084] In some embodiments, the bonding layer 20 is a transparent UV adhesive. UV adhesive, or ultraviolet light curable adhesive, is applied during dispensing to the gap between the annular surface 11 and the image-side surface of the flat optical element L0. Subsequently, ultraviolet light irradiation cures the adhesive, forming a transparent solid bonding layer 20. The advantages of using UV adhesive include its fast curing speed, ease of operation, and the good optical transparency and chemical stability of the cured adhesive layer, meeting the requirements for use in harsh environments such as high-temperature and high-pressure sterilization of endoscopes.

[0085] As a feasible implementation method, the field of view of the objective lens is greater than or equal to 70°.

[0086] The objective lens structure provided in this invention is applicable to applications with a large field of view. In particular, the contradiction between optical distortion and waterproof sealing is especially prominent at a field of view of 70° and above. This invention, by setting a concave central surface 10 and an approximately planar annular surface 11 on the objective side of the first lens L1, can effectively correct the distortion of the large field of view while achieving reliable bonding and waterproofing with the flat optical element L0, thus well balancing the needs of large field of view observation and waterproof reliability.

[0087] As a possible implementation method, such as Figures 1-6 As shown, the objective lens also includes a lens group G1 located on the image side of the first lens. The lens group G1 includes a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from the object side to the image side along the optical axis. The second lens L2 has positive optical power, the third lens L3 has negative optical power, and the fourth lens L4 has positive optical power.

[0088] The lens group G1 is used to further transmit and converge the light rays after they have been gathered by the first lens L1 onto the image plane.

[0089] In lens group G1, the second lens L2 has positive optical power, the third lens L3 has negative optical power, and the fourth lens L4 has positive optical power. The above combination of positive-negative-positive optical power can effectively correct the remaining various on-axis and off-axis aberrations of the system. Combined with the distortion correction function of the front-end first lens L1, the objective lens as a whole obtains good overall imaging quality at a large field of view.

[0090] As a possible implementation method, such as Figures 1-6 As shown, the third lens L3 and the fourth lens L4 form the first cemented lens g1.

[0091] By bonding the third lens L3 and the fourth lens L4 together, the reflection loss caused by the air gap between the third lens L3 and the fourth lens L4 can be effectively reduced, thereby improving the light transmittance.

[0092] Meanwhile, the introduction of the first cemented lens g1 helps to correct the chromatic aberration of the system and reduces the impact of the accumulated tolerances of multiple independent lens assembly on the imaging quality, thereby improving the overall optical performance and assembly stability of the objective lens.

[0093] It should be noted that the lens group G1 is not limited to the structure described above. The positive-negative-positive optical power combination composed of the second lens L2, the third lens L3, and the fourth lens L4 is merely an exemplary embodiment. Those skilled in the art can adjust and modify the number of lenses, optical power distribution, and whether or not they are cemented together, according to actual optical design requirements. As long as it can cooperate with the first lens L1 at the front end to achieve a large field of view and low distortion optical performance, it falls within the protection scope of this invention.

[0094] As a possible implementation method, such as Figures 1-6 As shown, the objective lens also includes an optical element 30 with no optical power, which is located in the optical path between the first lens L1 and the second lens L2.

[0095] Among them, the optical element 30 has zero optical power, and its object side and image side can both be flat, which plays the role of folding the optical path or equivalent flat plate in the optical system.

[0096] Optionally, the optical element 30 is a prism or equivalent plate, used to refract the light rays incident from the object side, so as to arrange the entire optical system in a limited space and adapt to the structural requirements of the slender endoscope tube.

[0097] For example, optical element 30 is a prism. The prism uses total internal reflection or reflective coating to fold the light path, which can compress the axial dimension of the system while maintaining the optical path length, which is beneficial to the design of the endoscope tube with a smaller diameter and more compact size.

[0098] For example, optical element 30 is an equivalent plate. The equivalent plate can be a transparent optical element with both the object side and the image side being flat. Its function is to provide a specific optical path length without changing the direction of the optical path, or to serve as a mounting reference for other optical elements.

[0099] Whether using a prism or an equivalent plate, since the optical element 30 has no optical power, it will not have a substantial impact on the focal length and aberration correction of the objective lens system, but it can provide the necessary flexibility for the structural layout of the optical system.

[0100] As a feasible implementation method, the absolute value of the optical distortion of the objective lens is less than or equal to 2%.

[0101] By using the aspherical design of the concave center surface 10 on the object side of the first lens L1, the present invention can effectively correct off-axis aberrations under a large field of view, and significantly reduce the optical distortion, which is usually as high as about 20% in conventional 70-degree field of view endoscopes, to less than 2%. The above-mentioned low distortion design can significantly improve the image distortion problem caused by distortion, enabling doctors to accurately observe the size and shape of lesions and improve the accuracy of clinical diagnosis.

[0102] It should be noted that the design of the annular surface 11 (approximately plane at the edge) of the present invention is not obvious. This is because, under a large field of view, in order to correct severe distortion, the edge of the aspherical surface usually needs to have a large bending and curvature change. However, the present invention does the opposite. Under the premise of ensuring that the central surface 10 has sufficient distortion correction capability, the annular surface 11 at the edge is set as an approximate plane with an absolute value of tangential angle not greater than 0.1° through precise optical design. This facilitates reliable surface-to-surface bonding with the flat optical element L0. This design breaks the conventional understanding of the edge surface shape of aspherical surfaces by those skilled in the art. While achieving low distortion of less than 2%, it also constructs a reliable bonding and waterproof structure, achieving a technological breakthrough.

[0103] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the magnifying lens applicable to the above-described embodiments.

[0104] Example 1 like Figure 1 and Figure 2 As shown, the objective lens of the endoscope provided in Embodiment 1 of the present invention includes a flat optical element L0, a first lens L1, an optical element 30, and a lens group G1 arranged sequentially from the object side to the image side along the optical axis. The lens group G1 includes a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from the object side to the image side along the optical axis. The third lens L3 and the fourth lens L4 form a first cemented lens g1.

[0105] Table 1 details the surface type, radius of curvature R, thickness D, refractive index Nd, and Abbe number Vd of each lens in the objective lens of the endoscope provided in the embodiment, according to a feasible implementation. The objectives in Table 1 correspond to... Figure 1 The objective lens shown.

[0106] Table 1 Design values ​​of the optical physical parameters of the objective lens In this table, the surface numbers are assigned according to the order of the lenses. For example, surface number "1" represents the object side of the flat optical element, surface number "2" represents the image side of the flat optical element, and so on. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value means that the surface bends towards the object surface, with the center of the circle closer to the image surface; a negative value means that the surface bends towards the image surface, with the center of the circle closer to the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness D represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. The Abbe number Vd refers to the dispersion characteristics of the material between the current surface and the next surface. "Air" indicates that the current position is air and the refractive index is 1.

[0107] In this embodiment, the aspherical conic coefficient of the aspherical lens can be defined using the following aspherical formula, but is not limited to the following representation: ; in, The axial sagitta in the Z-direction of the aspherical surface; It is half-caliber; To fit the curvature of the sphere, =1 / R, where R is the radius of curvature of the vertex of the aspherical surface; The conic coefficient; It is the aspherical coefficient.

[0108] For example, Table 2 details the aspherical coefficients of each lens in this embodiment with a feasible implementation method.

[0109] Table 2 Design values ​​of aspherical coefficients for each lens in the objective lens For example, Table 3 details, with a feasible implementation, the variation of the tangential angle θ of the object side of the first lens from the edge of the 85% field of view beam to the edge of the annular surface with half the aperture in this embodiment.

[0110] Table 3. Design values ​​of the tangential angle of the object side of the first lens from the edge of the beam at 85% field of view to the edge of the annular surface. Figure 27 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 1 of the present invention when the flat optical element and the first lens are not attached. Figure 28 The figure shows the MTF curve of the objective lens of the endoscope provided in Embodiment 1 of the present invention after the flat optical element and the first lens are bonded. The MTF curve can characterize the overall imaging quality of the objective lens. The higher the MTF value, the clearer the image. In the figure, the vertical direction is the normalized MTF value (OTF modulus value), 0 indicates no contrast, the vertical vertex represents the maximum contrast, and there is no unit; the horizontal direction is the X field of view, and the unit is degrees (°), which represents the angular position of the field of view from the center of the optical axis (0°) to the edge; the solid line represents the meridion, and the dashed line represents the arc. As can be seen from the figure, the modulation transfer function after the flat optical element and the first lens are bonded is basically the same as before the flat optical element and the first lens are bonded in most fields of view, and no significant decrease occurs; MTF degradation only occurs in the edge field of view area (outside 90% of the field of view), indicating that the introduction of the bonding layer 20 only has a limited impact on the image quality of the edge field of view, while the imaging quality in the main viewing area that the user is most concerned about is well maintained, which can ensure stable and excellent imaging quality in the main observation area.

[0111] Figure 29This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 1 of the present invention. In the left coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (without unit); T represents meridion, and S represents arc loss. As can be seen from the figure, the objective lens provided in this embodiment effectively controls the field curvature for light with a wavelength of 0.656 μm, that is, during imaging, the difference between the image quality in the center and the image quality at the periphery is small. In the right coordinate system, the horizontal axis represents the magnitude of the distortion in %; the vertical axis represents the normalized image height (without unit). As can be seen from the figure, the distortion of the objective lens provided in this embodiment is within 0.5%, which is well corrected, and the imaging distortion is small, meeting the requirements for low distortion.

[0112] Example 2 like Figure 3 and Figure 4 As shown, the objective lens of the endoscope provided in Embodiment 2 of the present invention includes a flat optical element L0, a first lens L1, an optical element 30, and a lens group G1 arranged sequentially from the object side to the image side along the optical axis. The lens group G1 includes a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from the object side to the image side along the optical axis. The third lens L3 and the fourth lens L4 form a first cemented lens g1.

[0113] Table 4 details the surface type, radius of curvature R, thickness D, refractive index Nd, and Abbe number Vd of each lens in the objective lens of the endoscope provided in the embodiment, according to a feasible implementation. The objectives in Table 4 correspond to... Figure 3 The objective lens shown.

[0114] Table 4 Design values ​​of the optical physical parameters of the objective lens In this table, the surface numbers are assigned according to the order of the lenses. For example, surface number "1" represents the object side of the flat optical element, surface number "2" represents the image side of the flat optical element, and so on. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value means that the surface bends towards the object surface, with the center of the circle closer to the image surface; a negative value means that the surface bends towards the image surface, with the center of the circle closer to the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness D represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. The Abbe number Vd refers to the dispersion characteristics of the material between the current surface and the next surface. "Air" indicates that the current position is air and the refractive index is 1.

[0115] In this embodiment, the aspherical conic coefficient of the aspherical lens can be defined using the following aspherical formula, but is not limited to the following representation: ; in, The axial sagitta in the Z-direction of the aspherical surface; It is half-caliber; To fit the curvature of the sphere, =1 / R, where R is the radius of curvature of the vertex of the aspherical surface; The conic coefficient; It is the aspherical coefficient.

[0116] For example, Table 5 details the aspherical coefficients of each lens in this embodiment with a feasible implementation method.

[0117] Table 5 Design values ​​of aspherical coefficients for each lens in the objective lens For example, Table 6 details, with a feasible implementation, the variation of the tangential angle θ of the object side of the first lens from the edge of the 85% field of view beam to the edge of the annular surface with half the aperture in this embodiment.

[0118] Table 6. Design values ​​of the tangential angle of the object side of the first lens from the edge of the 85% field of view beam to the edge of the annular surface. Figure 30 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 2 of the present invention when the flat optical element and the first lens are not attached. Figure 31 The figure shows the MTF curve of the objective lens of the endoscope provided in Embodiment 2 of the present invention after the flat optical element and the first lens are bonded. The MTF curve can characterize the overall imaging quality of the objective lens. The higher the MTF value, the clearer the image. In the figure, the vertical direction is the normalized MTF value (OTF modulus value), 0 indicates no contrast, the vertical vertex represents the maximum contrast, and there is no unit; the horizontal direction is the X field of view, and the unit is degrees (°), which represents the angular position of the field of view from the center of the optical axis (0°) to the edge; the solid line represents the meridion, and the dashed line represents the arc. As can be seen from the figure, the modulation transfer function after the flat optical element and the first lens are bonded is basically the same as before the flat optical element and the first lens are bonded in most fields of view, and no significant decrease occurs; MTF degradation only occurs in the edge field of view area (outside 90% of the field of view), indicating that the introduction of the bonding layer 20 only has a limited impact on the image quality of the edge field of view, while the imaging quality in the main viewing area that the user is most concerned about is well maintained, which can ensure stable and excellent imaging quality in the main observation area.

[0119] Figure 32This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 2 of the present invention. In the left coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (without units); the solid line represents the meridion, and the dashed line represents the arc distortion. As can be seen from the figure, the objective lens provided in this embodiment effectively controls the field curvature for light with a wavelength of 0.656 μm, that is, during imaging, the difference between the image quality in the center and the image quality at the periphery is small. In the right coordinate system, the horizontal axis represents the magnitude of the distortion in %; the vertical axis represents the normalized image height (without units). As can be seen from the figure, the distortion of the objective lens provided in this embodiment is within 1%, which is well corrected, and the imaging distortion is small, meeting the requirements for low distortion.

[0120] Example 3 like Figure 5 and Figure 6 As shown, the objective lens of the endoscope provided in Embodiment 3 of the present invention includes a flat optical element L0, a first lens L1, an optical element 30, and a lens group G1 arranged sequentially from the object side to the image side along the optical axis. The lens group G1 includes a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from the object side to the image side along the optical axis. The third lens L3 and the fourth lens L4 form a first cemented lens g1.

[0121] Table 7 details the surface type, radius of curvature R, thickness D, refractive index Nd, and Abbe number Vd of each lens in the objective lens of the endoscope provided in the embodiment, according to a feasible implementation. The objectives in Table 7 correspond to... Figure 5 The objective lens shown.

[0122] Table 7 Design values ​​of the optical physical parameters of the objective lens In this table, the surface numbers are assigned according to the order of the lenses. For example, surface number "1" represents the object side of the flat optical element, surface number "2" represents the image side of the flat optical element, and so on. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value means that the surface bends towards the object surface, with the center of the circle closer to the image surface; a negative value means that the surface bends towards the image surface, with the center of the circle closer to the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness D represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. The Abbe number Vd refers to the dispersion characteristics of the material between the current surface and the next surface. "Air" indicates that the current position is air and the refractive index is 1.

[0123] In this embodiment, the aspherical conic coefficient of the aspherical lens can be defined using the following aspherical formula, but is not limited to the following representation: ; in, The axial sagitta in the Z-direction of the aspherical surface; It is half-caliber; To fit the curvature of the sphere, =1 / R, where R is the radius of curvature of the vertex of the aspherical surface; The conic coefficient; It is the aspherical coefficient.

[0124] For example, Table 8 details the aspherical coefficients of each lens in this embodiment with a feasible implementation.

[0125] Table 8 Design values ​​of aspherical coefficients for each lens in the objective lens For example, Table 9 details, in one feasible implementation, the variation of the tangential angle θ of the object side of the first lens from the edge of the 85% field of view beam to the edge of the annular surface with half the aperture.

[0126] Table 9. Design values ​​of the tangential angle of the object side of the first lens from the edge of the 85% field of view beam to the edge of the annular surface. Figure 33 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 3 of the present invention when the flat optical element and the first lens are not attached. Figure 34 The figure shows the MTF curve of the objective lens of the endoscope provided in Embodiment 3 of the present invention after the flat optical element and the first lens are bonded. The MTF curve can characterize the overall imaging quality of the objective lens. The higher the MTF value, the clearer the image. In the figure, the vertical direction is the normalized MTF value (OTF modulus value), 0 indicates no contrast, the vertical vertex represents the maximum contrast, and there is no unit; the horizontal direction is the X field of view, and the unit is degrees (°), which represents the field of view angle position from the center of the optical axis (0°) to the edge; the solid line represents the meridion, and the dashed line represents the arc. As can be seen from the figure, the modulation transfer function after the flat optical element and the first lens are bonded is basically the same as before the flat optical element and the first lens are bonded in most fields of view, and no significant decrease occurs; MTF degradation only occurs in the edge field of view area (outside 100% of the field of view), indicating that the introduction of the bonding layer 20 only has a limited impact on the image quality of the edge field of view, while the imaging quality in the main viewing area that the user is most concerned about is well maintained, which can ensure stable and excellent imaging quality in the main observation area.

[0127] Figure 35This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 3 of the present invention. In the left coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (without units); the solid line represents the meridion, and the dashed line represents the arc distortion. As can be seen from the figure, the objective lens provided in this embodiment effectively controls the field curvature for light with a wavelength of 0.656 μm, that is, during imaging, the difference between the image quality in the center and the image quality at the periphery is small. In the right coordinate system, the horizontal axis represents the magnitude of the distortion in %; the vertical axis represents the normalized image height (without units). As can be seen from the figure, the distortion of the objective lens provided in this embodiment is within 1%, which is well corrected, and the imaging distortion is small, meeting the requirements for low distortion.

[0128] Example 4 like Figure 7 and Figure 8 As shown, the objective lens of the endoscope provided in Embodiment 4 of the present invention includes a flat optical element L0, a first lens L1, an optical element 30, and a lens group G1 arranged sequentially from the object side to the image side along the optical axis. The lens group G1 includes a second lens L2, a third lens L3, and a fourth lens L4 arranged sequentially from the object side to the image side along the optical axis. The third lens L3 and the fourth lens L4 form a first cemented lens g1.

[0129] Table 10 details the surface type, radius of curvature R, thickness D, refractive index Nd, and Abbe number Vd of each lens in the objective lens of the endoscope provided in the embodiment, according to a feasible implementation. The objectives in Table 10 correspond to... Figure 7 The objective lens shown.

[0130] Table 10 Design values ​​of the optical physical parameters of the objective lens In this table, the surface numbers are assigned according to the order of the lenses. For example, surface number "1" represents the object side of the flat optical element, surface number "2" represents the image side of the flat optical element, and so on. The radius of curvature R represents the curvature of the corresponding lens surface. A positive value means that the surface bends towards the object surface, with the center of the circle closer to the image surface; a negative value means that the surface bends towards the image surface, with the center of the circle closer to the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness D represents the central axial distance between the current surface and the next surface. The refractive index Nd represents the ability of the material between the current surface and the next surface to deflect light. The Abbe number Vd refers to the dispersion characteristics of the material between the current surface and the next surface. "Air" indicates that the current position is air and the refractive index is 1.

[0131] In this embodiment, the aspherical conic coefficient of the aspherical lens can be defined using the following aspherical formula, but is not limited to the following representation: ; in, The axial sagitta in the Z-direction of the aspherical surface; It is half-caliber; To fit the curvature of the sphere, =1 / R, where R is the radius of curvature of the vertex of the aspherical surface; The conic coefficient; It is the aspherical coefficient.

[0132] For example, Table 11 details the aspherical coefficients of each lens in this embodiment with a feasible implementation.

[0133] Table 11 Design values ​​of aspherical coefficients for each lens in the objective lens For example, Table 12 details, with a feasible implementation, the variation of the tangential angle θ of the object side of the first lens from the edge of the 85% field of view beam to the edge of the annular surface with half the aperture in this embodiment.

[0134] Table 12 Design values ​​of the tangential angle of the object side of the first lens from the edge of the beam at 85% field of view to the edge of the annular surface. Figure 36 This is an MTF curve of the objective lens of the endoscope provided in Embodiment 4 of the present invention when the flat optical element and the first lens are not attached. Figure 37 The figure shows the MTF curve of the objective lens of the endoscope provided in Embodiment 4 of the present invention after the flat optical element and the first lens are bonded. The MTF curve can characterize the overall imaging quality of the objective lens. The higher the MTF value, the clearer the image. In the figure, the vertical direction is the normalized MTF value (OTF modulus value), 0 indicates no contrast, the vertical vertex represents the maximum contrast, and there is no unit; the horizontal direction is the X field of view, and the unit is degrees (°), which represents the angular position of the field of view from the center of the optical axis (0°) to the edge; the solid line represents the meridion, and the dashed line represents the arc. As can be seen from the figure, the modulation transfer function after the flat optical element and the first lens are bonded is basically the same as before the flat optical element and the first lens are bonded in most fields of view, and no significant decrease occurs; MTF degradation only occurs in the edge field of view area (outside 90% of the field of view), indicating that the introduction of the bonding layer 20 only has a limited impact on the image quality of the edge field of view, while the imaging quality in the main viewing area that the user is most concerned about is well maintained, which can ensure stable and excellent imaging quality in the main observation area.

[0135] Figure 38This is a field curvature distortion diagram of the objective lens of the endoscope provided in Embodiment 4 of the present invention. In the left coordinate system, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height (without units); T represents the meridion, and S represents arc loss. As can be seen from the figure, the objective lens provided in this embodiment effectively controls the field curvature for light with a wavelength of 0.656 μm, that is, during imaging, the difference between the image quality in the center and the image quality at the periphery is small. In the right coordinate system, the horizontal axis represents the magnitude of the distortion in %; the vertical axis represents the normalized image height (without units). As can be seen from the figure, the distortion of the objective lens provided in this embodiment is within 2%, which is well corrected, and the imaging distortion is small, meeting the requirements for low distortion.

[0136] To provide a clearer explanation of the above embodiments, Table 13 details the specific optical physical parameters of each lens in the objective lens of the endoscope provided in Embodiments 1 to 4 of the present invention.

[0137] Table 13 Design values ​​of the optical physical parameters of the objective lens Among them, the edge half-aperture of the 85% field of view beam refers to the incident height of the edge ray corresponding to the 85% field of view angle on the object side of the first lens L1, that is, the radial distance from the edge of the beam to the optical axis.

[0138] The edge half-aperture of the 100% field of view beam refers to the incident height of the edge ray corresponding to the maximum field of view on the object side of the first lens L1, that is, the radial distance from the outer boundary of the effective light-passing area to the optical axis, also known as the effective half-aperture.

[0139] The percentage of the field of view where significant image degradation occurs refers to the location in the image where image quality is significantly degraded due to the light beam passing through both air and adhesive media simultaneously. It is expressed as a percentage of the entire field of view. For example, a value of 0.9 indicates that the degradation occurs at 90% of the field of view. The closer the value is to 1, the closer the degraded area is to the edge of the image, and the smaller its impact on the user's subjective experience.

[0140] The maximum and minimum difference of the tangential angle of the annular surface refers to the absolute value of the difference between the largest and smallest tangential angles θ at all positions on the annular surface 11. This parameter characterizes the fluctuation range of the tangential angle θ on the annular surface 11. In all embodiments, it is controlled within 0.1° to ensure that the annular surface 11 has a highly consistent surface flatness throughout the entire annular region.

[0141] The maximum absolute value of the tangential angle of the annular surface refers to the largest absolute value of the tangential angle θ among all positions on the annular surface 11. This parameter characterizes the maximum deviation of the annular surface 11 from the ideal plane. In all embodiments, this value is no greater than 0.09°, which meets the design requirement of no more than 0.1°.

[0142] The width of the annular surface, i.e., the radial width of the annular surface 11, is the difference between the outer radius and the inner radius of the annular surface 11. This width directly determines the radial bonding length of the adhesive layer 20. The larger the width, the longer the waterproof sealing path and the stronger the waterproof capability.

[0143] The percentage of the annular surface occupying half the edge of the beam in 100% of the field of view refers to the percentage of the radial width of the annular surface 11 divided by the effective half-aperture. In each embodiment, this percentage satisfies a design constraint of not less than 37.8%, ensuring sufficient dispensing width within a limited radial space.

[0144] The effective thickness increase ratio of the bonding layer refers to the improvement in the radial bonding width of the bonding layer 20 (i.e., the radial width of the annular surface 11) in this invention compared to the existing non-bonded solutions that rely solely on the thickness of the flat optical element L0 as a waterproof barrier. For example, when the thickness of the flat optical element L0 is 0.3 mm, if the width of the annular surface 11 is 0.418 mm, the effective thickness increase ratio is 0.418 / 0.3 = 139%. This parameter directly reflects the degree of enhancement in waterproof reliability.

[0145] The objective lens of the endoscope provided by this invention, by setting an aspherical surface with functional partitions on the object-side surface of the first lens L1, namely a concave central surface 10 in the central region and an approximately planar annular surface 11 in the edge region, reduces the absolute value of optical distortion of the large field-of-view endoscope from approximately 20% to less than 2%, significantly improving the image distortion problem caused by distortion, enabling doctors to accurately observe the size and shape of lesions. Simultaneously, the approximately planar design of the annular surface 11 and the image-side surface of the flat optical element L0 achieve reliable surface-to-surface bonding through the bonding layer 20, significantly increasing the effective thickness of the waterproof adhesive from only equal to the thickness of the flat optical element itself to the radial width of the annular surface 11, with an effective thickness increase of over 100%, significantly enhancing the waterproof reliability of the objective lens under harsh environments such as high-temperature and high-pressure sterilization. Thus, it achieves a balance between a large field of view, low optical distortion, and excellent waterproof performance.

[0146] Based on the same inventive concept, this invention also provides an endoscope, which includes the objective lens of the endoscope described in any embodiment of this invention. Therefore, the endoscope provided by this invention has the technical effects of the technical solutions in any of the above embodiments. The explanations of the same or corresponding structures and terms as described in the above embodiments will not be repeated here.

[0147] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0148] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An objective lens of an endoscope, characterized by, It includes a flat optical element and a first lens arranged sequentially along the optical axis from the object side to the image side; The first lens is a glass lens, the first lens has negative optical power, and the object side of the first lens is aspherical; The object-side surface of the first lens includes a central surface located in the central region and an annular surface surrounding the central surface. The central surface is concave, and the absolute value of the tangential angle of the annular surface at each position is less than or equal to 0.1°. Wherein, the tangential angle is the angle between the tangent plane at any position within the annular surface and the plane perpendicular to the optical axis; At least a portion of the annular surface is located in the effective light-transmitting area; The image-side surface of the flat optical element is bonded to the annular surface via an adhesive layer.

2. The objective lens according to claim 1, characterized in that, The absolute value of the difference between the largest and smallest tangential angles at each position of the annular surface is less than or equal to 0.1°.

3. The objective lens according to claim 1, characterized in that, The inner radius of the annular surface is greater than or equal to 85% of the maximum field-of-view beam aperture on the object side of the first lens.

4. The objective lens according to claim 1, characterized in that, The radial width of the annular surface is greater than or equal to 37.8% of the effective half-aperture of the object side of the first lens.

5. The objective lens according to claim 1, characterized in that, The thickness of the bonding layer is less than or equal to 0.01 mm.

6. The objective lens according to claim 1, characterized in that, The objective lens has a field of view greater than or equal to 70°.

7. The objective lens according to claim 1, characterized in that, The objective lens also includes a lens group located on the image side of the first lens; The lens group includes a second lens, a third lens, and a fourth lens arranged sequentially from the object side to the image side along the optical axis; The second lens has positive optical power, the third lens has negative optical power, and the fourth lens has positive optical power.

8. The objective lens according to claim 7, characterized in that, The third lens and the fourth lens together form the first cemented lens.

9. The objective lens according to claim 7, characterized in that, It also includes optical elements without optical power; The optical element is located in the optical path between the first lens and the second lens.

10. An endoscope, characterized in that, The objective lens of the endoscope as described in any one of claims 1-9.

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