A side-viewing endoscope

Abstract

This invention discloses a side-viewing endoscope, comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the object plane to the image plane. The first lens has negative optical power; the third lens has positive optical power; the fourth lens has positive optical power; and the fifth lens has negative optical power. The second lens is a right-angle prism, with the image-side surface of the first lens and the object-side surface of the third lens corresponding to two 45-degree planes of the right-angle prism, respectively. By rationally setting the optical power of the first, third, fourth, and fifth lenses, the side-viewing endoscope can achieve the requirements of wide viewing angle and high-resolution imaging while maintaining miniaturization.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and more particularly to a side-viewing endoscope. Background Technology

[0002] Industrial endoscopes, for example, are often used for non-destructive testing of areas that are difficult to observe directly, such as the interior of metal components and bends in pipes. These applications impose strict limitations on the outer diameter of the endoscope probe while simultaneously requiring the largest possible field of view, typically exceeding 80°, and high-resolution imaging. Furthermore, when observing lateral areas, the lens must have a 90° viewing angle, meaning the light path bends 90° within the probe. However, currently available industrial endoscopes on the market cannot simultaneously meet all these requirements. Summary of the Invention

[0003] This invention provides a side-viewing endoscope that, while ensuring miniaturization, meets the requirements of a 90° viewing angle, a large field of view, and high-resolution imaging.

[0004] The present invention provides a side-viewing endoscope, comprising a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged sequentially along the optical axis from the object plane to the image plane; the side-viewing endoscope has four lenses with optical power. The first lens has negative optical power; the third lens has positive optical power; the fourth lens has positive optical power; and the fifth lens has negative optical power. The second lens is a right-angle prism, and the image-side of the first lens and the object-side of the third lens correspond to the two 45-degree planes of the right-angle prism, respectively.

[0005] Optionally, the object-side surface of the first lens is concave, and the image-side surface of the first lens is planar. The object-side surface of the third lens is a plane, and the image-side surface of the third lens is a convex surface; The object-side surface of the fourth lens is convex, and the image-side surface of the fourth lens is convex. The object-side surface of the fifth lens is concave, and the image-side surface of the fifth lens is also concave.

[0006] Optionally, the first lens, the third lens, the fourth lens, and the fifth lens are all glass spherical lenses.

[0007] Optionally, the fourth lens and the fifth lens are cemented together to form a cemented lens group.

[0008] Optionally, the diagonal field of view of the side-viewing endoscope is FOV, the effective focal length of the side-viewing endoscope is F, and the image height corresponding to the maximum field of view of the side-viewing endoscope is IMGH1, wherein... 100° < FOV < 140°, 0.54 < F / IMGH1 < 0.62.

[0009] Optionally, the maximum outer diameter of the structure of the side-view endoscope lens is φ, where 1.8 mm < φ < 2.1 mm.

[0010] Optionally, the focal length of the first lens is F1, the focal length of the third lens is F3, the curvature radius of the object side surface of the first lens at the optical axis is R1, the curvature radius of the image side surface of the third lens at the optical axis is R6, half of the maximum effective aperture of the object side surface of the first lens is SD1, and half of the maximum effective aperture of the image side surface of the third lens is SD6, where -1.75 < F1 / F3 < -1.39, and / or, 1.89 < |R1 / R6| < 2.17, and / or, 0.56 < SD1 / SD6 < 0.88.

[0011] Optionally, the curvature radius of the image side surface of the fourth lens at the optical axis is R8, the focal length of the fourth lens is F4, the thickness of the fourth lens on the optical axis is CT4, the distance in the optical axis direction from the maximum effective aperture of the object side surface of the fourth lens to the maximum effective aperture of the image side surface of the fourth lens is ET4, and half of the maximum effective aperture of the image side surface of the fourth lens is SD8, where 1.00 < R8 / F4 < 1.11, and / or, 2.33 < CT4 / ET4 < 4.38, and / or, 0.89 < SD8 / CT4 < 1.15.

[0012] Optionally, the full-field modulation transfer function of the side-view endoscope lens is MTF, where MTF > 0.2 @ 200 lp / mm.

[0013] Optionally, the side-view endoscope lens further includes an aperture; The aperture is located in the optical path between the second lens and the third lens.

[0014] The side-view endoscope lens of the technical solution of the embodiment of the present invention includes a first lens, a second lens, a third lens, a fourth lens, and a fifth lens arranged in sequence along the optical axis from the object surface to the image surface; the second lens is a right-angle prism, which realizes total reflection and turning of light rays to obtain a 90° viewing angle. The optical powers of the first lens, the third lens, the fourth lens, and the fifth lens are reasonably set to ensure that the side-view endoscope lens can meet the requirements of large viewing angle and high-resolution imaging on the premise of miniaturization.

[0015] 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

[0016] 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.

[0017] Figure 1 This is a schematic diagram of the structure of a side-viewing endoscope provided in an embodiment of the present invention; Figure 2 A front view of a side-view endoscope provided in an embodiment of the present invention; Figure 3 This is an MTF chart of a side-viewing endoscope provided in Embodiment 1 of the present invention; Figure 4 A relative illumination diagram of a side-view endoscope provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the structure of a side-viewing endoscope provided in Embodiment 2 of the present invention; Figure 6 This is an MTF chart of a side-viewing endoscope provided in Embodiment 2 of the present invention; Figure 7 This is a relative illumination diagram of a side-view endoscope provided in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the structure of a side-viewing endoscope provided in Embodiment 3 of the present invention; Figure 9 This is an MTF chart of a side-viewing endoscope provided in Embodiment 3 of the present invention; Figure 10 This is a relative illumination diagram of a side-view endoscope provided in Embodiment 3 of the present invention. Detailed Implementation

[0018] 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.

[0019] 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 a 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.

[0020] Figure 1 This is a schematic diagram of the structure of a side-view endoscope provided in an embodiment of the present invention. Figure 2 A front view of a side-view endoscope provided in an embodiment of the present invention, such as... Figure 1 and Figure 2 As shown, the side-viewing endoscope includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, and a fifth lens 105 arranged sequentially along the optical axis from the object plane to the image plane; the side-viewing endoscope has four lenses with optical power; the first lens 101 has negative optical power; the third lens 103 has positive optical power; the fourth lens 104 has positive optical power; the fifth lens 105 has negative optical power; the second lens 102 is a right-angle prism, and the image-side surface of the first lens 101 and the object-side surface of the third lens 103 correspond to the two 45-degree planes of the right-angle prism, respectively.

[0021] Optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens, or a system formed by multiple lenses (i.e., a lens group). In the side-view endoscope provided in this embodiment, each lens can be fixed to a single lens barrel (…). Figure 1Within the optical system (not shown), a first lens 101 with negative optical power is used to control the incident angle and expand the field of view. A second lens 102 is a right-angle prism. The image-side surface of the first lens 101 and the object-side surface of the third lens 103 correspond to the two 45-degree faces of the right-angle prism. The physical properties of a high-refractive-index material are used to achieve total internal reflection of the light rays, resulting in a 90° viewing angle. This allows the light rays output from the first lens 101 to be redirected 90° by the second lens 102 before entering the third lens 103. The third lens 103 has positive optical power and can correct the spherical aberration produced by the first lens 101. A fourth lens 104 has positive optical power; a fifth lens 105 has negative optical power and can effectively correct the field curvature of the optical system. By combining the optical powers of the fourth lens 104 and the fifth lens 105, chromatic aberration can be optimized. In the optical system provided in this application, by rationally allocating the optical power of each lens, the phenomenon of excessive refraction of light on a certain lens is effectively suppressed, thereby reducing the sensitivity of this optical system to processing tolerances, assembly tolerances, etc., and improving lens resolution and production yield.

[0022] Optionally, the object-side surface of the first lens 101 is concave, and the image-side surface of the first lens 101 is planar; the object-side surface of the third lens 103 is planar, and the image-side surface of the third lens 103 is convex; the object-side surface of the fourth lens 104 is convex, and the image-side surface of the fourth lens 104 is convex; the object-side surface of the fifth lens 105 is concave, and the image-side surface of the fifth lens 105 is concave.

[0023] In this context, the object-side surface of a lens can be understood as the surface of the lens closest to the object plane, and the image-side surface can be understood as the surface of the lens closest to the image plane. The object-side surface of the first lens 101 is concave, and the image-side surface of the first lens 101 is flat; that is, the object-side surface of the first lens 101 convexes towards the image plane near the optical axis, making it a plano-convex lens. The object-side surface of the third lens 103 is flat, and the image-side surface of the third lens 103 is convex; that is, the image-side surface of the third lens 103 convexes towards the image plane near the optical axis, making it a plano-convex lens. The object-side surface of the fourth lens 104... The fourth lens 104 has a convex image-side surface, meaning its object-side surface bulges towards the object plane near the optical axis, and its image-side surface bulges towards the image plane near the optical axis. Therefore, the fourth lens 104 is a biconvex lens. Similarly, the fifth lens 105 has a concave image-side surface, meaning its object-side surface bulges towards the image plane near the optical axis, and its image-side surface bulges towards the object plane near the optical axis. Therefore, the fifth lens 105 is a biconcave lens. By appropriately setting the surface shape of each lens and combining it with their optical power, the imaging effect of the side-viewing endoscope can be further adjusted.

[0024] Optionally, the first lens 101, the third lens 103, the fourth lens 104 and the fifth lens 105 are all glass spherical lenses.

[0025] Among them, spherical lenses are characterized by a constant curvature from the center to the periphery, and their manufacturing process is simple, allowing them to be produced using traditional cold-working techniques. Furthermore, due to the low coefficient of thermal expansion and good stability of glass lenses, the first lens 101, third lens 103, fourth lens 104, and fifth lens 105 can all be made of glass spherical lenses. Glass spherical lenses exhibit excellent high and low temperature defocusing performance; within a temperature range from room temperature to 120℃, the lens's resolving power does not significantly deteriorate. In addition, compared to plastic aspherical lenses, glass offers a wider range of material choices, with more freedom in selecting the refractive index and Abbe number, allowing for better control of higher-order aberrations and meeting the needs of use under complex conditions.

[0026] Optionally, the fourth lens 104 and the fifth lens 105 are cemented together to form a cemented lens group.

[0027] By cementing the image-side surface of the fourth lens 104 with the object-side surface of the fifth lens 105, the fourth lens 104 and the fifth lens 105 can be combined into a cemented lens. Using a cemented lens effectively reduces the air gap between the fourth lens 104 and the fifth lens 105, thereby reducing the overall length of the lens. Furthermore, cemented lenses can be used to minimize or eliminate chromatic aberration, allowing for sufficient correction of various aberrations in side-view endoscopes. This improves resolution and optimizes optical performance such as distortion and CRA while maintaining a compact structure. It also reduces light loss caused by inter-lens reflections, increasing illumination and thus improving image quality and lens image sharpness. In addition, the use of cemented lenses reduces the number of assembly components between the two lenses, simplifying the assembly process in lens manufacturing, reducing costs, and minimizing tolerance sensitivity issues such as tilting / eccentricity of the lens unit during assembly.

[0028] Optionally, the diagonal field of view of the side-viewing endoscope is FOV, the effective focal length of the side-viewing endoscope is F, and the image height corresponding to the maximum field of view of the side-viewing endoscope is IMGH1, where 100° <FOV<140°,0.54<F / IMGH1<0.62。

[0029] Among them, the field of view angle FOV of the side-view endoscope lens satisfies 100° < FOV < 140°. The side-view endoscope lens provided by the embodiment of the present invention is a side-view endoscope lens with a large field of view angle, meeting the requirement of a large field of view. The effective focal length F of the side-view endoscope lens and the image height IMGH1 corresponding to the maximum field of view angle of the side-view endoscope lens satisfy 0.54 < F / IMGH1 < 0.6. By restricting the ratio of the focal length to the image height of the side-view endoscope lens, it is beneficial for the side-view endoscope lens to have the characteristic of a large image plane while meeting miniaturization requirements to meet imaging needs.

[0030] Optionally, the maximum outer diameter of the structure of the side-view endoscope lens is φ, where 1.8 mm < φ < 2.1 mm.

[0031] Among them, as Figure 2 shown, the outer diameter of the side-view endoscope is jointly determined by the outer diameter of the first lens 101 and the maximum outer diameter among the third lens 103, the fourth lens 104, and the fifth lens 105. To achieve a small outer diameter of the lens, it is necessary to select appropriate outer diameters of the first lens 101 and the maximum outer diameter among the third lens 103, the fourth lens 104, and the fifth lens 105 to form a lens with a small outer diameter. By reasonably setting the maximum outer diameter φ of the side-view endoscope lens to satisfy 1.8 mm < φ < 2.1 mm, the miniaturized design of the side-view endoscope lens is achieved.

[0032] Optionally, the focal length of the first lens 101 is F1, the focal length of the third lens 103 is F3, the curvature radius of the object side surface of the first lens 101 at the optical axis is R1, the curvature radius of the image side surface of the third lens 103 at the optical axis is R6, half of the maximum effective aperture of the object side surface of the first lens 101 is SD1, and half of the maximum effective aperture of the image side surface of the third lens 103 is SD6, where -1.75 < F1 / F3 < -1.39, and / or, 1.89 < |R1 / R6| < 2.17, and / or, 0.56 < SD1 / SD6 < 0.88.

[0033] Among them, when F1 / F3 is close to -1.75, the outer diameter of the first lens 101 is smaller than the outer diameters of the third lens 103, the fourth lens 104, and the fifth lens 105. At this time, the outer diameter of the lens can be minimized, that is, an outer diameter of 1.8 mm; when F1 / F3 is close to -1.39, the outer diameter of the first lens 101 is larger than the outer diameters of the third lens 103, the fourth lens 104, and the fifth lens 105. At this time, the outer diameter of the lens is relatively large, that is, an outer diameter of 2.1 mm, but it is still within an acceptable range, meeting the miniaturized design of the side-view endoscope lens.

[0034] The curvature radius R1 of the object side of the first lens 101 at the optical axis and the curvature radius R6 of the image side of the third lens 103 at the optical axis satisfy 1.89 < |R1 / R6| < 2.17. Reasonably setting the bending degrees of the first lens 101 and the third lens 103 is beneficial to the miniaturization design of the side-view endoscope lens. At the same time, by optimizing the shapes of the first lens 101 and the third lens 103, it is beneficial to improve the imaging quality of the side-view endoscope lens.

[0035] Half of the maximum effective aperture SD1 of the object side of the first lens 101 and half of the maximum effective aperture SD6 of the image side of the third lens 103 satisfy 0.56 < SD1 / SD6 < 0.88, so that the third lens 103 has the characteristic of a small aperture, can effectively converge the light rays of the first lens 101, and make the light rays better enter the imaging surface of the lens, ensuring the imaging quality.

[0036] Optionally, the curvature radius of the image side of the fourth lens 104 at the optical axis is R8, the focal length of the fourth lens 104 is F4, the thickness of the fourth lens 104 on the optical axis is CT4, the distance in the optical axis direction from the maximum effective aperture of the object side of the fourth lens 104 to the maximum effective aperture of the image side of the fourth lens 104 is ET4, and half of the maximum effective aperture of the image side of the fourth lens 104 is SD8, where 1.00 < R8 / F4 < 1.11, and / or, 2.33 < CT4 / ET4 < 4.38, and / or, 0.89 < SD8 / CT4 < 1.15.

[0037] Among them, setting the curvature radius R8 of the image side of the fourth lens 104 at the optical axis and the focal length F4 of the fourth lens 104 to satisfy 1.00 < R8 / F4 < 1.11 can effectively improve the aberration of the marginal field of view and enhance the overall imaging quality of the lens by setting the fourth lens 104 to have a relatively large positive optical power. At the same time, reasonably limiting the focal length and the surface shape of the image side of the fourth lens 104 is beneficial to converging light rays while reducing the deflection angle of the light rays, shortening the distance for the light rays to reach the next lens, and is beneficial to reducing the total length of the side-view endoscope lens.

[0038] Setting the thickness CT4 of the fourth lens 104 on the optical axis and the distance ET4 in the optical axis direction from the maximum effective aperture of the object side of the fourth lens 104 to the maximum effective aperture of the image side of the fourth lens 104 to satisfy 2.33 < CT4 / ET4 < 4.38, by setting the ratio relationship between the central thickness and the edge thickness of the fourth lens 104, on the basis of meeting the current cold processing level, it can effectively balance the high-order aberration generated by the optical lens, and is also beneficial to the field curvature adjustment of the fourth lens 104, thereby improving the imaging quality of the side-view endoscope lens.

[0039] Set half of the maximum effective aperture SD8 of the image side of the fourth lens 104 and the thickness CT4 of the fourth lens 104 on the optical axis to satisfy 0.89 < SD8 / CT4 < 1.15, which can enable the fourth lens 104 to accurately control the light propagation angle and convergence path during the light refraction process, greatly reduce the interference of aberration such as spherical aberration and coma, and significantly improve the light convergence efficiency and imaging clarity of the side-view endoscope lens.

[0040] Optionally, the full-field modulation function of the side-view endoscope lens is MTF, where MTF > 0.2 @ 200 lp / mm.

[0041] Among them, the full-field modulation function is a key parameter describing the ability of the lens to reproduce object details. The higher the MTF value, the stronger the ability of the lens to transfer the image contrast, and the clearer the imaging. The full-field modulation function MTF of the side-view endoscope lens provided by the present invention is greater than 20% at 200 lp / mm, ensuring that the side-view endoscope lens has the ability to resolve extremely fine features and ensuring the imaging clarity.

[0042] Optionally, the side-view endoscope lens further includes an aperture (not shown in the figure); the aperture is located in the optical path between the second lens 102 and the third lens 103.

[0043] Among them, by adding an aperture, the propagation direction of the light beam can be adjusted, which is beneficial to improving the imaging quality. The aperture can be located in the optical path between the second lens 102 and the third lens 103. Reasonably setting the position of the aperture can control the outer diameter size of the front and rear lenses, but the specific setting position of the aperture in the embodiments of the present invention is not limited.

[0044] Optionally, a filter 106 is further provided along the object surface to the image surface; the filter 106 is located on the image side of the fifth lens 105.

[0045] Among them, by setting the filter 106 between the fifth lens 105 and the image surface, unwanted stray light is filtered out, thereby improving the image quality of the side-view endoscope lens. For example, the imaging quality of the side-view endoscope lens is improved by filtering out infrared light through the filter 106 during the day.

[0046] Optionally, a chip protection glass 107 is further provided along the object surface to the image surface; the chip protection glass 107 is located on the image side of the filter 106.

[0047] In this embodiment, by providing the chip protection glass 107 on the image side of the filter 106 to protect the photosensitive chip in the imaging sensor, where the imaging chip is used to convert the optical signal collected by the side-view endoscope lens into an electrical signal, thereby ensuring the imaging effect of the side-view endoscope lens.

[0048] The side-viewing endoscope provided in this embodiment of the invention, by reasonably allocating the optical power, surface shape, radius of curvature, focal length, thickness, etc. of each lens, and by matching it with a right-angle prism, satisfies a 90° viewing angle, and ensures the balance of the incident angle of the front and rear lens groups of the side-viewing endoscope under the premise of miniaturization, reduces the sensitivity of the lens, and achieves the requirements of a large field of view and high-resolution imaging.

[0049] The following describes in further detail, with reference to the accompanying drawings, specific embodiments of the side-view endoscope applicable to the above-described embodiments.

[0050] Example 1 Continue to refer to Figure 1 The side-viewing endoscope includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, and a fifth lens 105 arranged sequentially along the optical axis from the object plane to the image plane. The second lens 102 is a right-angle prism, and the image-side surface of the first lens 101 and the object-side surface of the third lens 103 correspond to the two 45-degree planes of the right-angle prism, respectively. An aperture stop is positioned in the optical path between the second lens 102 and the third lens 103. Table 1 shows the surface type, radius of curvature, thickness, and material, among other optical and physical parameters, of each lens in the side-viewing endoscope provided in Embodiment 1.

[0051] Table 1 Optical and physical parameters of side-viewing endoscopes The surface numbers are assigned according to the order of the lenses. For example, surfaces numbered 1 and 2 are the object-side and image-side surfaces of the first lens 101, respectively; surfaces numbered 3 and 4 are the 45-degree surfaces of the second lens 102, respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the central axial distance between the current surface and the next surface; both the radius of curvature and thickness are in millimeters (mm). The refractive index represents the ability of the material between the current and next surfaces to deflect light; a space indicates that the current location is air and the refractive index is 1. The Abbe number represents the dispersion characteristics of the material between the current and next surfaces; a space indicates that the current location is air.

[0052] The side-view endoscope in this embodiment one achieves the following technical specifications: Focal length: f=1.32mm; Aperture number: F=6.

[0053] Figure 3The MTF chart of a side-view endoscope provided in Embodiment 1 of the present invention shows the normalized value of the modulation transfer function on the vertical axis, which directly reflects the system's ability to transfer image details and contrast. The horizontal axis represents the spatial frequency, with units of line pairs per millimeter (lp / mm). At 200 line pairs / mm, the transfer function in the MTF curve is generally above 0.2. The curves indicate that at this frequency, the MTF value of the system across the entire field of view is greater than 0.2. The curves for each field of view are flat and converge, proving that the entire lens possesses good and consistent modulation contrast reproduction characteristics across the entire image plane, meeting the imaging requirements of high-resolution displays.

[0054] Figure 4 This is a relative illumination diagram of a side-viewing endoscope provided in Embodiment 1 of the present invention. The vertical axis represents relative illumination, and the horizontal axis represents the field of view. Relative illumination is used to describe the brightness uniformity of the image plane from the center to the edge. Figure 4 As shown, the relative illuminance reflects the uniformity of the lens's image illumination. When the field of view is 50°, the relative illuminance can be higher than 75%, which means it has high relative illuminance and sufficient light intake. This ensures that even when the lens is used in a relatively dark environment, there will be no dark corners at the edges of the actual image, thus ensuring consistent visual perception.

[0055] Example 2 Figure 5 This is a schematic diagram of the structure of a side-viewing endoscope provided in Embodiment 2 of the present invention, as shown below. Figure 5 As shown, the side-viewing endoscope includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, and a fifth lens 205 arranged sequentially along the optical axis from the object plane to the image plane. The second lens 202 is a right-angle prism, and the image-side surface of the first lens 201 and the object-side surface of the third lens 203 correspond to the two 45-degree planes of the right-angle prism, respectively. An aperture stop is positioned in the optical path between the second lens 202 and the third lens 203. Table 2 shows the optical physical parameters of each lens in the side-viewing endoscope provided in Embodiment 2, including surface type, radius of curvature, thickness, and material.

[0056] Table 2 Optical and physical parameters of side-viewing endoscopes The surface numbers are assigned according to the order of the lenses. For example, surfaces numbered 1 and 2 are the object-side and image-side surfaces of the first lens 201, respectively; surfaces numbered 3 and 4 are the 45-degree surfaces of the second lens 202, respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image plane, and a negative value indicates that the surface bends towards the object plane. "Infinity" indicates that the surface is flat and has an infinite radius of curvature. Thickness represents the central axial distance between the current surface and the next surface; both the radius of curvature and thickness are in millimeters (mm). Refractive index represents the ability of the material between the current and next surfaces to deflect light; a space indicates that the current location is air and the refractive index is 1. Abbe number represents the dispersion characteristics of the material between the current and next surfaces; a space indicates that the current location is air.

[0057] The side-view endoscope in this second embodiment achieves the following technical specifications: Focal length: f=1.21mm; Aperture number: F=6.

[0058] Figure 6 The MTF chart for a side-view endoscope provided in Embodiment 2 of the present invention shows the normalized value of the modulation transfer function on the vertical axis, which directly reflects the system's ability to transfer image details and contrast. The horizontal axis represents the spatial frequency, with units of line pairs per millimeter (lp / mm). At 200 line pairs / mm, the transfer function in the MTF curve is generally above 0.2. The curves indicate that at this frequency, the MTF value of the system across the entire field of view is greater than 0.2. The curves for each field of view are flat and converge, proving that the entire lens possesses good and consistent modulation contrast reproduction characteristics across the entire image plane, meeting the imaging requirements of high-resolution displays.

[0059] Figure 7 This is a relative illumination diagram of a side-viewing endoscope provided in Embodiment 2 of the present invention. The vertical axis represents relative illumination, and the horizontal axis represents the field of view. Relative illumination is used to describe the brightness uniformity of the image plane from the center to the edge. Figure 7 As shown, the relative illuminance reflects the uniformity of the lens's image illumination. When the field of view is 54.9°, the relative illuminance can be higher than 80%, which means it has high relative illuminance and sufficient light intake. This ensures that even when the lens is used in a relatively dark environment, there will be no dark corners at the edges of the actual image, thus ensuring consistent visual perception.

[0060] Example 3 Figure 8 This is a schematic diagram of the structure of a side-viewing endoscope provided in Embodiment 3 of the present invention, as shown below. Figure 8As shown, the side-viewing endoscope includes a first lens 201, a second lens 202, a third lens 203, a fourth lens 204, and a fifth lens 205 arranged sequentially along the optical axis from the object plane to the image plane. The second lens 202 is a right-angle prism, and the image-side surface of the first lens 201 and the object-side surface of the third lens 203 correspond to the two 45-degree planes of the right-angle prism, respectively. An aperture stop is positioned in the optical path between the second lens 202 and the third lens 203. Table 3 shows the optical physical parameters of each lens in the side-viewing endoscope provided in Embodiment 3, including surface type, radius of curvature, thickness, and material.

[0061] Table 3 Optical and physical parameters of side-viewing endoscopes The surface numbers are assigned according to the order of the lenses. For example, surfaces numbered 1 and 2 are the object-side and image-side surfaces of the first lens 301, respectively; surfaces numbered 3 and 4 are the 45-degree surfaces of the second lens 302, respectively, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates the surface bends towards the image plane, and a negative value indicates the surface bends towards the object plane. "Infinity" indicates the surface is flat with an infinite radius of curvature. Thickness represents the axial distance between the current surface and the next surface; both radius of curvature and thickness are in millimeters (mm). Refractive index represents the ability of the material between the current and next surfaces to deflect light; a space indicates the current location is air with a refractive index of 1. Abbe number represents the dispersion characteristics of the material between the current and next surfaces; a space indicates the current location is air.

[0062] The side-view endoscope in this embodiment three achieves the following technical specifications: Focal length: f=1.08mm; Aperture number: F=6.

[0063] Figure 9 The MTF chart for a side-view endoscope provided in Embodiment 3 of the present invention shows the normalized value of the modulation transfer function on the vertical axis, which directly reflects the system's ability to transfer image details and contrast. The horizontal axis represents the spatial frequency, with units of line pairs per millimeter (lp / mm). At 200 line pairs / mm, the transfer function in the MTF curve is generally above 0.2. The curves indicate that at this frequency, the MTF value of the system across the entire field of view is greater than 0.2. The curves for each field of view are flat and converge, proving that the entire lens possesses good and consistent modulation contrast reproduction characteristics across the entire image plane, meeting the imaging requirements of high-resolution displays.

[0064] Figure 10This is a relative illumination diagram of a side-viewing endoscope provided in Embodiment 3 of the present invention. The vertical axis represents relative illumination, and the horizontal axis represents the field of view. Relative illumination is used to describe the brightness uniformity of the image plane from the center to the edge. Figure 10 As shown, the relative illuminance reflects the uniformity of the lens's image illumination. When the field of view is 69.7°, the relative illuminance can be higher than 85%, which means it has high relative illuminance and sufficient light intake. This ensures that even when the lens is used in a relatively dark environment, there will be no dark corners at the edges of the actual image, thus ensuring the consistency of visual perception.

[0065] 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. A side-viewing endoscope head, characterized by, There are a first lens, a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence from the object plane to the image plane along the optical axis; the number of lenses with optical power in the side-view endoscope lens is four; The first lens has a negative optical power; the third lens has a positive optical power; the fourth lens has a positive optical power; the fifth lens has a negative optical power; The second lens is a right-angle prism, and the image side of the first lens and the object side of the third lens respectively correspond to two 45-degree surfaces of the right-angle prism.

2. The side-view endoscope lens according to claim 1, wherein The object side of the first lens is a concave surface, and the image side of the first lens is a flat surface; The object side of the third lens is a flat surface, and the image side of the third lens is a convex surface; The object side of the fourth lens is a convex surface, and the image side of the fourth lens is a convex surface; The object side of the fifth lens is a concave surface, and the image side of the fifth lens is a concave surface.

3. The side-viewing endoscope according to claim 1, characterized in that, The first lens, the third lens, the fourth lens and the fifth lens are all glass spherical lenses.

4. The side-viewing endoscope according to claim 1, characterized in that, The fourth lens and the fifth lens are glued and fixed to form a glued lens group.

5. The side-viewing endoscope according to claim 1, characterized in that, The diagonal field angle of the side-view endoscope lens is FOV, the effective focal length of the side-view endoscope lens is F, and the image height corresponding to the maximum field angle of the side-view endoscope lens is IMGH1, where 100° < FOV < 140°, 0.54 < F / IMGH1 < 0.

62.

6. The side-viewing endoscope according to claim 1, characterized in that, The maximum outer diameter of the structure of the side-view endoscope lens is φ, where 1.8 mm < φ < 2.1 mm.

7. The side-viewing endoscope according to claim 1, characterized in that, The focal length of the first lens is F1, the focal length of the third lens is F3, the radius of curvature of the object side of the first lens at the optical axis is R1, the radius of curvature of the image side of the third lens at the optical axis is R6, and half of the maximum effective aperture of the object side of the first lens is SD1, and half of the maximum effective aperture of the image side of the third lens is SD6, where -1.75 < F1 / F3 < -1.39, and / or, 1.89 < |R1 / R6| < 2.17, and / or, 0.56 < SD1 / SD6 < 0.

88.

8. The side-viewing endoscope according to claim 1, characterized in that, The radius of curvature of the image side of the fourth lens at the optical axis is R8, the focal length of the fourth lens is F4, the thickness of the fourth lens on the optical axis is CT4, the distance in the optical axis direction from the maximum effective aperture of the object side of the fourth lens to the maximum effective aperture of the image side of the fourth lens is ET4, and half of the maximum effective aperture of the image side of the fourth lens is SD8, where 1.00 < R8 / F4 < 1.11, and / or, 2.33 < CT4 / ET4 < 4.38, and / or, 0.89 < SD8 / CT4 < 1.

15.

9. The side-viewing endoscope according to claim 1, characterized in that, The full-field modulation transfer function of the side-view endoscope lens is MTF, where MTF > 0.2 @ 200 lp / mm.

10. The side-viewing endoscope according to claim 1, characterized in that, The side-view endoscope lens further includes an aperture; The aperture is located in the optical path between the second lens and the third lens.

Images