Endoscope head, endoscope imaging system

Abstract

The present disclosure provides an endoscope lens, an endoscope imaging system, which comprises: a first lens, a first prism, a second lens, a third lens, a fourth lens glued with the third lens, and a fifth lens arranged in sequence from the object side to the image side, wherein the first lens is a glass aspheric negative lens, the image side surface of the first lens is a concave surface; the second lens has positive tortuosity, the image side surface of the second lens is a convex surface; the third lens has positive tortuosity, the object side surface of the third lens is a convex surface; the fourth lens has negative tortuosity, the image side surface of the fourth lens is a concave surface; the fifth lens is a glass aspheric positive lens, the object side surface of the fifth lens is a convex surface, and the image side surface of the fifth lens is a convex surface, so that the imaging of the endoscope lens can have good image quality.

Description

Technical Field

[0001] This disclosure relates to the field of optical components, and in particular to an endoscope lens and an endoscope imaging system. Background Technology

[0002] Optical lenses have a wide range of applications, including traditional professional camera equipment, the explosively growing mobile phone lenses, vehicle surveillance lenses, emerging AR and VR lenses for smart home or wearable devices, and miniature lenses for inspecting industrial equipment.

[0003] In the medical field, due to the difficulty in observing internal human tissues, medical endoscopes have been designed to probe the body and observe for lesions, thus facilitating better treatment plans. Endoscopic imaging systems are also used in minimally invasive surgery. Minimally invasive surgery offers numerous advantages, including less trauma to the patient, reduced intraoperative pain, and shorter postoperative recovery time. Therefore, a high-performance endoscopic imaging system would greatly aid in the implementation of procedures such as diagnosis and treatment, and minimally invasive surgery.

[0004] Optical lenses are essential components in various imaging systems, directly affecting the quality of images and even the implementation and effectiveness of algorithms. Summary of the Invention

[0005] In view of this, it is necessary to provide an endoscope to address the above-mentioned problems, thereby solving at least one of the problems of existing lenses, such as large aperture, small field of view, large distortion, and large chromatic aberration.

[0006] This disclosure provides an endoscope comprising: a first lens, a first prism, a second lens, a third lens, a fourth lens cemented to the third lens, and a fifth lens arranged sequentially from the object side to the image side. The first lens is a glass aspherical negative lens, and the image side of the first lens is concave. The second lens has positive refractive power, and the image side of the second lens is convex. The third lens has positive refractive power, and the object side of the third lens is convex. The fourth lens has negative refractive power, and the image side of the fourth lens is concave. The fifth lens is a glass aspherical positive lens, and the object side of the fifth lens is convex, and the image side of the fifth lens is convex.

[0007] This configuration, with the first lens being a glass aspherical negative lens, helps to increase the field of view of the endoscope and reduce its aperture. Combined with other lenses, it achieves a small-aperture, large-field-of-view endoscope. In addition to the first lens, a fifth lens, a glass aspherical positive lens, is also configured. The aspherical surface of the mirror can increase the lens's degree of freedom, thereby effectively improving the relative illumination of the endoscope. It can also reduce the number of lenses required for the same performance to a certain extent. At the same time, various low-refractive-index, high-dispersion glass materials can be selected, which is more flexible than the actual selection of plastic materials. This further improves the performance of the endoscope.

[0008] Alternating combinations of lenses with positive and negative refractive forces help balance aberrations across different fields of view and effectively correct astigmatism, chromatic aberration, and distortion, ensuring that the acquired image data is suitable for conversion and achieving three-dimensional effects. Furthermore, cemented lenses can better correct chromatic aberration, allowing the endoscope to achieve good chromatic aberration characteristics over a wider wavelength range, including the visible and fluorescent ranges.

[0009] In some embodiments, the first prism is detachably connected to the second lens, and the first lens is detachably connected to the second lens.

[0010] With this configuration, at least five lenses combined can achieve good imaging results, and the cementation of the third and fourth lenses can further reduce chromatic aberration. Furthermore, the endoscope provided in this embodiment allows for the replacement of the first prism by configuring the first prism to be detachably and rotatably connected to the second lens, and the first lens to be detachably connected to the first prism.

[0011] In some embodiments, the endoscope further includes a second prism, the second prism having a different orientation angle relative to the optical axis than the first prism; the second prism is interchangeable with the first prism.

[0012] This configuration allows for the installation of multiple prisms with different turning angles, enabling the endoscope to observe fields of view at different angles by replacing different prisms. Furthermore, by switching prisms, the endoscope can observe the object side at directions such as 0° or 30° relative to the imaging optical axis, and can also observe a circumferential image at, for example, a 30° direction.

[0013] In some embodiments, the second lens is a glass aspherical lens or a glass spherical lens, the third lens is a glass aspherical lens or a glass spherical lens, and the fourth lens is a glass aspherical lens or a glass spherical lens.

[0014] This setup allows for more flexible selection of the materials for the three lenses. Setting the mirror surface to spherical can reduce costs while ensuring imaging performance. In some cases, it can ensure that the modulus of the modulation transfer function of the 0.7 field of view is greater than 0.3 under the condition of 160 lp / mm. Setting the mirror surface to aspherical will further enhance the freedom of endoscope design and improve image quality.

[0015] In some embodiments, the object-side surface of the first lens is convex or concave.

[0016] With this configuration, the object-side surface of the first lens is convex, which helps to collect object-side light and ensure the field of view, while the object-side surface of the first lens is concave, which facilitates the installation of the endoscope.

[0017] In some embodiments, the object side surface of the second lens is convex, flat or concave.

[0018] With this arrangement, since the first prism is replaceable, by controlling the surface shape of the object side surface of the second lens, the imaging effect of the subsequent lens can be ensured. Exemplarily, when the object side surface of the second lens is flat, it can better cooperate with the first prism at its front end during the assembly process and reduce the assembly tolerance. Exemplarily, when the object side surface of the second lens is convex or concave, it is beneficial to reduce the coma and astigmatism of the endoscope lens, and at the same time, it is also beneficial to compress the incident angle of the light at the aperture position, thereby better controlling the shape and size of the distortion.

[0019] In some embodiments, the effective focal length f1 of the first lens satisfies: -2.3 mm < f1 < -1.5 mm; the effective focal length f2 of the second lens satisfies: 5.0 mm < f2 < 6.5 mm.

[0020] With this arrangement, the optical power of the first lens and the optical power of the second lens can be effectively controlled within a reasonable range, so that both of them bear the optical power required by the endoscope lens, and the spherical aberration contributed by both of them is within a reasonable and controllable range, ensuring better image quality in the axial field of view. In addition, the relative illumination of the endoscope lens can be ensured, and at least the relative illumination of the marginal field of view can be improved within the visible light range.

[0021] In some embodiments, the field of view FOV of the endoscope lens satisfies: FOV ≥ 80°.

[0022] With this arrangement, by configuring a larger field of view, a larger range can be better observed in the endoscope working environment.

[0023] In some embodiments, the absolute value of the distortion of the endoscope lens in the direction of the imaging face diagonal is less than 6%.

[0024] With this arrangement, by controlling the absolute value of the distortion of the endoscope lens, an accurate image can be better observed, which helps to more accurately judge the state of the observed part.

[0025] In some embodiments, the effective focal length f3 of the third lens satisfies: 3.5 mm < f3 < 20.0 mm; the effective focal length f4 of the fourth lens satisfies: -30.0 mm < f4 < -2.0 mm.

[0026] With this arrangement, the cemented third lens and fourth lens can be better applied to light with wavelengths of 430 nm to 880 nm.

[0027] In some embodiments, the effective focal length f5 of the fifth lens satisfies: 2.5 mm < f5 < 5 mm.

[0028] This configuration allows for a certain degree of control over the contribution rate of spherical aberration and astigmatism of the fifth lens, thereby balancing the astigmatism and spherical aberration generated by the front and rear optical lenses of the endoscope, resulting in good imaging quality for the endoscope.

[0029] In some implementations, the relative illumination RI of the edge field of view of the endoscope lens satisfies: RI > 80%.

[0030] This setup ensures relative illumination at the edges of the field of view, thereby enabling clearer images to be obtained in endoscopic working environments.

[0031] In some embodiments, the optical path t12 from the image-side surface of the first lens to the object-side surface of the second lens satisfies: 4 mm <t12<5mm。

[0032] With this configuration, the first prism positioned between the first lens and the second lens has good design flexibility, and the first prism can be configured to meet different needs.

[0033] In some embodiments, the maximum diameter of each of the first to fifth lenses and the first prism is less than 3.2 mm.

[0034] This configuration, by controlling the dimensions of each component of the endoscope, allows for a better reduction in the endoscope's aperture, while ensuring that each lens has sufficient design space to guarantee image quality.

[0035] In some implementations, the total effective focal length f of the endoscope lens satisfies: f < 1.9 mm.

[0036] This setup ensures that the endoscopic lens has a small focal length, thereby achieving a large depth of field range and good imaging results under different object distance conditions.

[0037] In some embodiments, the first prism includes a steering prism, the light output direction of which is adapted to the optical axis of the second lens, and the light input direction of which is adapted to the optical axis of the first lens, wherein the light output direction of the steering prism intersects with the light input direction.

[0038] With this configuration, by setting up a steering prism, the endoscope can view the center of the field of view in the direction where the imaging optical axes intersect.

[0039] In some embodiments, the steering prism includes: an incident surface; a first functional layer for transmitting light incident through the incident surface; a second functional layer for reflecting light transmitted through the first functional layer back to the first functional layer, wherein the first functional layer is also used to reflect light reflected by the second functional layer; and an exiting surface for transmitting light reflected by the first functional layer.

[0040] This configuration ensures that the optical path length within the first prism meets the design value and achieves good light transmission for imaging.

[0041] In some embodiments, the endoscope further includes a quarter-wave plate located between the first functional layer and the second functional layer; and wherein the first functional layer includes a polarizing beam splitter.

[0042] This configuration ensures that the light passing through the polarizing beam splitter is polarized, avoiding interference from light on the incident side of the beam splitter. Furthermore, the quarter-wave plate prevents mutual interference between light on the output side of the beam splitter, thus preserving the image information carried by the light transmitted through the steering prism. This results in good image quality for the endoscope.

[0043] On the other hand, this disclosure provides an endoscopic imaging system, including: the aforementioned endoscopic lens; and an imaging chip located on the imaging surface of the endoscopic lens.

[0044] This configuration, through the aforementioned endoscope lens, allows for a larger field of view within a confined space. Furthermore, this endoscopic imaging system can also obtain brighter images.

[0045] In some embodiments, the endoscopic imaging system also includes a protective glass located on the first lens object side.

[0046] This design allows the protective glass to withstand different endoscopic environments and to allow light to pass through, enabling the endoscope to work effectively for a long time. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the structure of the endoscope in an embodiment of this disclosure;

[0048] Figure 2 It shows Figure 1 The on-axis chromatic aberration curve of the endoscope lens shown;

[0049] Figure 3 It shows Figure 1 The relative illumination curve of the endoscope lens is shown.

[0050] Figure 4 It shows Figure 1 The modulation transfer function curve of the endoscope lens is shown.

[0051] Figure 5 It shows Figure 1 The astigmatism curve of the endoscope lens shown;

[0052] Figure 6 It shows Figure 1 The distortion curve of the endoscope shown;

[0053] Figure 7This is a schematic diagram of another structure of the endoscope lens according to an embodiment of the present disclosure;

[0054] Figure 8 for Figure 7 A magnified schematic diagram of the first prism in the middle;

[0055] Figure 9 for Figure 8 Enlarged view of point A in the middle;

[0056] Figure 10 This is a schematic diagram of the structure of an endoscope lens according to another embodiment of the present disclosure;

[0057] Figure 11 It shows Figure 10 The on-axis chromatic aberration curve of the endoscope lens shown;

[0058] Figure 12 It shows Figure 10 The relative illumination curve of the endoscope lens is shown.

[0059] Figure 13 It shows Figure 10 The modulation transfer function curve of the endoscope lens is shown.

[0060] Figure 14 It shows Figure 10 The astigmatism curve of the endoscope lens shown;

[0061] Figure 15 It shows Figure 10 The distortion curve of the endoscope shown;

[0062] Figure 16 This is a schematic diagram of the structure of an endoscope lens according to another embodiment of the present disclosure;

[0063] Figure 17 It shows Figure 16 The on-axis chromatic aberration curve of the endoscope lens shown;

[0064] Figure 18 It shows Figure 16 The relative illumination curve of the endoscope lens is shown.

[0065] Figure 19 It shows Figure 16 The modulation transfer function curve of the endoscope lens is shown.

[0066] Figure 20 It shows Figure 16 The astigmatism curve of the endoscope lens shown;

[0067] Figure 21 It shows Figure 16 The distortion curve of the endoscope shown;

[0068] Figure 22This is a schematic diagram of the structure of an endoscope lens according to another embodiment of the present disclosure;

[0069] Figure 23 It shows Figure 22 The on-axis chromatic aberration curve of the endoscope lens shown;

[0070] Figure 24 It shows Figure 22 The relative illumination curve of the endoscope lens is shown.

[0071] Figure 25 It shows Figure 22 The modulation transfer function curve of the endoscope lens is shown.

[0072] Figure 26 It shows Figure 22 The astigmatism curve of the endoscope lens shown;

[0073] Figure 27 It shows Figure 22 The distortion curve of the endoscope shown;

[0074] Figure 28 This is a schematic diagram of the structure of an endoscope lens according to another embodiment of the present disclosure;

[0075] Figure 29 It shows Figure 28 The on-axis chromatic aberration curve of the endoscope lens shown;

[0076] Figure 30 It shows Figure 28 The relative illumination curve of the endoscope lens is shown.

[0077] Figure 31 It shows Figure 28 The modulation transfer function curve of the endoscope lens is shown.

[0078] Figure 32 It shows Figure 28 The astigmatism curve of the endoscope lens shown;

[0079] Figure 33 It shows Figure 28 The distortion curve of the endoscope is shown.

[0080] Reference numerals: P1, protective glass; P2, first lens; P3, first prism; P3', second prism; P31, first mirror body; P32, second mirror body; P33, third mirror body; P4, third lens; P5, third lens; P6, fourth lens; P7, fifth lens; P8, third prism; P9, filter; S0, imaging plane; S1, object-side surface of the first lens; S2, image-side surface of the first lens; S3, incident surface; S4, exit surface; S5, object-side surface of the second lens; S6 S7. Image-side surface of the second lens; S8. Object-side surface of the third lens; S9. Cemented surface; S10. Image-side surface of the fourth lens; S11. Object-side surface of the fifth lens; S12. Object-side surface of the third prism; S13. Image-side surface of the third prism; S14. Image-side surface of the filter; S15. First functional layer; S151. First dielectric layer; S152. Adhesive layer; S153. Second dielectric layer; S16. Second functional layer; X1. Imaging optical axis; X2. Linear optical axis. Detailed Implementation

[0081] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0082] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0083] The structural dimensions shown in the accompanying drawings in this article do not represent actual dimensions and may be adjusted as needed during actual production. The directional terms "up," "down," "left," and "right" used in this article refer to the orientation shown in the drawings and should not be considered as limitations on the actual use of the product unless explicitly stated otherwise.

[0084] In this article, the terms "first," "second," "third," etc., are used only to distinguish those with the same features. Understandably, the first lens in this article can also be called the second lens, and the second lens can also be called the first lens.

[0085] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. For example, the mirrors and their parameters referred to herein, unless explicitly limited, describe the near-optical axis portion. The terminology used herein in the specification of this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0086] like Figure 1 As shown, this embodiment of the present disclosure provides an endoscope, which includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. Figure 1 As shown, the imaging optical axis X1 is perpendicular to the imaging plane S0. Protective glass P1 to filter P9 can be arranged sequentially from the object side to the image side along the imaging optical axis X1.

[0087] The first lens P2 may have negative refractive power, and its material may be glass. The object-side surface S1 of the first lens may be convex, and the image-side surface S2 of the first lens may be concave. Specifically, the mirror surface of the first lens P2 may be aspherical. The second lens P4 may have positive refractive power, and its material may be glass. The object-side surface S5 of the second lens may be flat, and the image-side surface S6 of the second lens may be convex. Specifically, the mirror surface of the second lens P4 may be spherical. The third lens P5 and the fourth lens P6 are cemented together to form a cemented doublet spherical lens. Specifically, the third lens P5 may have positive refractive power, and its material may be glass. The object-side surface S7 of the third lens may be convex. The fourth lens P6 may have negative refractive power, and its material may be glass. The image-side surface S9 of the fourth lens may be concave. The object-side surface S7 of the third lens, the cemented surface S8, and the image-side surface S9 of the fourth lens may all be spherical. The fifth lens P7 may have positive refractive power, and its material may be glass. The object side S10 of the fifth lens may be convex, and the image side S11 of the fifth lens may be convex. Specifically, the mirror surface of the fifth lens P7 is aspherical.

[0088] The first prism P3 is used to transmit light passing through the first lens P2 to the second lens P4. The first prism P3 includes an incident surface S3 and an exit surface S4, which are perpendicular to the imaging optical axis X1. The third prism P8 can be made of glass. The object-side surface S12 of the third prism can be flat, and the image-side surface S13 of the third prism can be flat and fitted with the filter P9. The image-side surface S14 of the filter can be flat. The aperture stop S0 can be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 passes sequentially through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then forms an image on the imaging surface S0.

[0089] Figure 1 The endoscopic lens shown has a field of view (FOV) of 80° and a total effective focal length (f) of 1.87. Table 1 below shows the parameters of this endoscopic lens, where the units for radius of curvature, distance, and effective focal length are mm.

[0090] Table 1

[0091] Face number Surface type radius of curvature distance Refractive index Abbe number Effective focal length P1 object side spherical endless 0.5500 1.77 72.24 S1 aspherical 66.0120 0.4000 1.77 47.17 -2.09 S2 aspherical 1.5710 0.4885 S3 spherical endless 4.2000 2.0 24.44 S4 spherical endless 0.0300 STO spherical endless 0.3000 1.92 18.89 6.39 S5 spherical endless 0.7350 S6 spherical -5.9000 0.7580 S7 spherical 6.1760 1.1120 1.59 68.35 17.35 S8 spherical -6.1760 0.4800 1.84 23.78 -28.30 S9 spherical 6.1760 0.2842 S10 aspherical 5.0770 1.2670 1.49 82.51 4.69 S11 aspherical -2.3320 2.7064 S12 spherical endless 3.3000 1.76 52.34 S13 spherical endless 0.4000 1.52 64.21 S14 spherical endless 0.0370 S0 endless

[0092] The conic coefficients and higher-order coefficients A4, A6, A8 and A10 satisfied by the aspherical surface shape in the endoscope are shown in Table 2.

[0093] Table 2

[0094]

[0095] Figure 2 The on-axis chromatic aberration curve of the endoscope is shown. Figure 3 The relative illumination curve of the endoscope is shown. Figure 4 The modulation transfer function curve of the endoscope is shown. Figure 5 The astigmatism curve of the endoscope is shown. Figure 6 The distortion curve of the endoscope is shown. The relative illumination (RI) of the endoscope is greater than 0.8, and the MTFS and MTFT within a 0.7 field of view are both greater than 0.3 at 160 lp / mm. In addition, it exhibits good resistance to distortion and chromatic aberration.

[0096] For example, the first prism P3 and the second lens P4 of the endoscope are detachably connected, and the first lens P2 and the second lens P4 are also detachably connected. Specifically, the first lens P2 and the second lens P4 are indirectly connected through the first prism P3.

[0097] like Figure 7 As shown, the endoscope may also include a second prism P3'. Exemplarily, the second prism P3' and the first prism P3 can be used interchangeably, and the second prism P3' and the first prism P3 have the same optical path. In other embodiments, the endoscope may be considered to include only the second prism P3', and thus may be referred to as the first prism.

[0098] For example, the endoscope may include multiple sets of protective glass P1 and a first lens P2, one set of protective glass P1 and the first lens P2 being fixedly connected to a first prism P3, and another set of protective glass P1 and the first lens P2 being fixedly connected to a second prism P3'.

[0099] The second prism P3' is a steering prism, and the perpendicular line of its incident surface S3 is parallel to the directional optical axis X2 of the first lens P2. The directional optical axis X2 intersects the imaging optical axis X1, for example, at a 30° angle. By configuring the first lens P2, the first prism P3, and the second prism P3' to be detachably connected relative to the second lens P4, the endoscope can detect fields of view at different angles.

[0100] like Figure 8 As shown, the second prism P3' includes a first mirror body P31, a second mirror body P32, and a third mirror body P33. The first mirror body P31 includes an incident light surface S3. The second mirror body P32 is bonded to the first mirror body P31 and includes an exit light surface S4. The third mirror body P33 is bonded to the side of the second mirror body P32 facing away from the first mirror body P31. The second prism P3' also includes a first functional layer S15 located between the second mirror body P32 and the first mirror body P31, and a second functional layer S16 located between the second mirror body P32 and the third mirror body P33. Light incident along the optical axis X2 can pass through the first mirror body P31 and the first functional layer S15, enter the second mirror body P32, and be directed towards the second functional layer S16. The second functional layer S16 can reflect the light passing through the first functional layer S15 back to the first functional layer S15. The first functional layer S15 can reflect the light reflected by the second functional layer S16 towards the exit light surface S4. For example, light undergoes total internal reflection at the second functional layer S16 and the first functional layer S15. Further, the first functional layer S151 and the first mirror P31 are used together for total internal reflection of light, and the second functional layer S16 and the third mirror P31 are used together for total internal reflection of light.

[0101] For example, such as Figure 9 As shown, the first functional layer S15 includes a first dielectric layer S151, an adhesive layer S152, and a second dielectric layer S153 sequentially disposed from the first mirror body P31 to the second mirror body P32. The first dielectric layer S151 can be deposited on the first mirror body P31, and the second dielectric layer S153 can be deposited on the second mirror body P32, and then the two are bonded together by the adhesive layer S152. There can be no air gap between the first mirror body P31 and the second mirror body P32, resulting in better temperature resistance of the second prism P3'. The endoscope can maintain its performance even at high temperatures of up to 134°C. In addition, the second prism P3' has good impact resistance and high reliability.

[0102] For example, the material of the first dielectric layer S151 includes aluminum oxide (such as Al3O2), and the material of the second dielectric layer S153 includes silicon oxide (such as SiO2). The material of the second functional layer S16 may include a metal. In other embodiments, the first dielectric layer S151 includes a polarizing beam-splitting dielectric film, and the second dielectric layer S153 includes a quarter-wave plate.

[0103] In some embodiments, the first functional layer S15 includes a polarizing beam splitting medium film, and a quarter-wave plate is disposed between the first functional layer S15 and the second functional layer S16.

[0104] In the endoscopic lens provided in this embodiment, the first prism can also make the viewing optical axis and the imaging optical axis form other angles. For example, the third prism can be set as a right-angle prism.

[0105] Figure 10 Another endoscope according to an embodiment of this disclosure is shown. The endoscope includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging plane S0. The protective glass P1 to the filter P9 are arranged sequentially along the imaging optical axis from the object side to the image side.

[0106] The first lens P2 may have negative refractive power, and its material may be glass. The object-side surface S1 of the first lens may be concave, and the image-side surface S2 of the first lens may also be concave. Specifically, the mirror surface of the first lens P2 may be aspherical and may have a point of inflection. The second lens P4 may have positive refractive power, and its material may be glass. The object-side surface S5 of the second lens may be flat, and the image-side surface S6 of the second lens may be convex. Specifically, the mirror surface of the second lens P4 may be spherical. The third lens P5 and the fourth lens P6 are cemented together to form a cemented doublet spherical lens. Specifically, the third lens P5 may have positive refractive power, and its material may be glass. The object-side surface S7 of the third lens may be convex. The fourth lens P6 may have negative refractive power, and its material may be glass. The image-side surface S9 of the fourth lens may be concave. The object-side surface S7 of the third lens, the cemented surface S8, and the image-side surface S9 of the fourth lens may all be spherical. The fifth lens P7 may have positive refractive power, and its material may be glass. The object side S10 of the fifth lens may be convex, and the image side S11 of the fifth lens may be convex. Specifically, the mirror surface of the fifth lens P7 is aspherical.

[0107] The first prism P3 is used to transmit light passing through the first lens P2 to the second lens P4. The first prism P3 includes an incident surface S3 and an exit surface S4, which can be perpendicular to the imaging optical axis. The third prism P8 can be made of glass. The object-side surface S12 of the third prism can be flat, and the image-side surface S13 of the third prism can be flat and attached to the filter P9. The image-side surface S14 of the filter can be flat. The aperture stop S0 can be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 can pass sequentially through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then form an image on the imaging plane S0.

[0108] Figure 10The endoscopic lens shown has a field of view (FOV) of 80° and a total effective focal length (f) of 1.88. Table 3 below shows the parameters of this endoscopic lens, where the units for radius of curvature, distance, and effective focal length are mm.

[0109] Table 3

[0110]

[0111]

[0112] The conic coefficients and higher-order coefficients A4, A6, A8 and A10 satisfied by the aspherical surface shape in the endoscope are shown in Table 4.

[0113] Table 4

[0114]

[0115] Figure 11 The on-axis chromatic aberration curve of the endoscope is shown. Figure 12 The relative illumination curve of the endoscope is shown. Figure 13 The modulation transfer function curve of the endoscope is shown. Figure 14 The astigmatism curve of the endoscope is shown. Figure 15 The distortion curve of the endoscope is shown. The relative illumination (RI) of the endoscope is greater than 0.8, and the MTFS and MTFT within a 0.7 field of view are both greater than 0.3 at 160 lp / mm. In addition, it exhibits good resistance to distortion and chromatic aberration.

[0116] For example, the first prism P3 and the second lens P4 of the endoscope are detachably connected, and the first lens P2 and the second lens P4 are also detachably connected. Specifically, the first lens P2 and the second lens P4 are indirectly connected through the first prism P3.

[0117] Figure 16 Another endoscope according to an embodiment of this disclosure is shown. The endoscope includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging plane S0. The protective glass P1 to the filter P9 are arranged sequentially along the imaging optical axis from the object side to the image side.

[0118] The first lens P2 may have negative refractive power, and its material may be glass. The object-side surface S1 of the first lens may be convex, and the image-side surface S2 of the first lens may be concave. The second lens P4 may have positive refractive power, and its material may be glass. The object-side surface S5 of the second lens may be convex, and the image-side surface S6 of the second lens may be convex. Specifically, the mirror surface of the second lens P4 may be spherical. The third lens P5 and the fourth lens P6 are cemented together to form a cemented doublet spherical lens. Specifically, the third lens P5 may have positive refractive power, and its material may be glass. The object-side surface S7 of the third lens may be convex. The fourth lens P6 may have negative refractive power, and its material may be glass. The image-side surface S9 of the fourth lens may be concave. The object-side surface S7 of the third lens, the cemented surface S8, and the image-side surface S9 of the fourth lens may all be spherical. The fifth lens P7 may have positive refractive power, and its material may be glass. The object side S10 of the fifth lens may be convex, and the image side S11 of the fifth lens may be convex. Specifically, the mirror surface of the fifth lens P7 is aspherical.

[0119] The first prism P3 is used to transmit light passing through the first lens P2 to the second lens P4. The first prism P3 includes an incident surface S3 and an exit surface S4, which can be perpendicular to the imaging optical axis. The third prism P8 can be made of glass. The object-side surface S12 of the third prism can be flat, and the image-side surface S13 of the third prism can be flat and attached to the filter P9. The image-side surface S14 of the filter can be flat. The aperture stop S0 can be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 can pass sequentially through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then form an image on the imaging plane S0.

[0120] Figure 16 The endoscopic lens shown has a field of view (FOV) of 80° and a total effective focal length (f) of 1.88. Table 5 below shows the parameters of this endoscopic lens, where the units for radius of curvature, distance, and effective focal length are mm.

[0121] Table 5

[0122] Face number Surface type radius of curvature distance Refractive index Abbe number Effective focal length P1 object side spherical endless 0.5500 1.77 72.24 S1 aspherical 6.8811 0.3995 1.77 47.17 -1.89 S2 aspherical 1.2191 0.5195 S3 spherical endless 4.2000 2.0 24.44 S4 spherical endless 0.0300 STO spherical endless 0.3000 1.92 18.89 5.61 S5 spherical 75.3675 0.7464 S6 spherical -5.6868 0.6718 S7 spherical 4.6604 1.4038 1.59 68.35 4.16 S8 spherical -4.6604 0.7809 1.84 23.78 -2.23 S9 spherical 4.6604 0.1532 S10 aspherical 3.6276 1.6935 1.49 82.51 3.10 S11 aspherical -2.2695 3.0003 S12 spherical endless 3.3000 1.76 52.34 S13 spherical endless 0.3000 1.52 64.21 S14 spherical endless 0.0450 S0 endless

[0123] The conic coefficients and higher-order coefficients A4, A6, A8 and A10 satisfied by the aspherical surface shape in the endoscope are shown in Table 6.

[0124] Table 6

[0125]

[0126] Figure 17 The on-axis chromatic aberration curve of the endoscope is shown. Figure 18 The relative illumination curve of the endoscope is shown. Figure 19The modulation transfer function curve of the endoscope is shown. Figure 20 The astigmatism curve of the endoscope is shown. Figure 21 The distortion curve of the endoscope is shown. The relative illumination (RI) of the endoscope is greater than 0.8, and the MTFS and MTFT within the 0.7 field of view are both good at 160 lp / mm. In addition, it has good resistance to distortion and chromatic aberration.

[0127] For example, the first prism P3 and the second lens P4 of the endoscope are detachably connected, and the first lens P2 and the second lens P4 are also detachably connected. Specifically, the first lens P2 and the second lens P4 are indirectly connected through the first prism P3.

[0128] Figure 22 Another endoscope according to an embodiment of this disclosure is shown. The endoscope includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging plane S0. The protective glass P1 to the filter P9 are arranged sequentially along the imaging optical axis from the object side to the image side.

[0129] The first lens P2 may have negative refractive power, and its material may be glass. The object-side surface S1 of the first lens may be convex, and the image-side surface S2 of the first lens may be concave. The second lens P4 may have positive refractive power, and its material may be glass. The object-side surface S5 of the second lens may be concave, and the image-side surface S6 of the second lens may be convex. Specifically, the mirror surface of the second lens P4 may be spherical. The third lens P5 and the fourth lens P6 are cemented together to form a cemented doublet spherical lens. Specifically, the third lens P5 may have positive refractive power, and its material may be glass. The object-side surface S7 of the third lens may be convex. The fourth lens P6 may have negative refractive power, and its material may be glass. The image-side surface S9 of the fourth lens may be concave. The object-side surface S7 of the third lens, the cemented surface S8, and the image-side surface S9 of the fourth lens may all be spherical. The fifth lens P7 may have positive refractive power, and its material may be glass. The object side S10 of the fifth lens may be convex, and the image side S11 of the fifth lens may be convex. Specifically, the mirror surface of the fifth lens P7 is aspherical.

[0130] The first prism P3 is used to transmit light passing through the first lens P2 to the second lens P4. The first prism P3 includes an incident surface S3 and an exit surface S4, which can be perpendicular to the imaging optical axis. The third prism P8 can be made of glass. The object-side surface S12 of the third prism can be flat, and the image-side surface S13 of the third prism can be flat and attached to the filter P9. The image-side surface S14 of the filter can be flat. The aperture stop S0 can be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 can pass sequentially through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then form an image on the imaging plane S0.

[0131] Figure 22 The endoscopic lens shown has a field of view (FOV) of 80° and a total effective focal length (f) of 1.88. Table 7 below shows the parameters of this endoscopic lens, where the units for radius of curvature, distance, and effective focal length are mm.

[0132] Table 7

[0133] Face number Surface type radius of curvature distance Refractive index Abbe number Effective focal length P1 object side spherical endless 0.5500 1.77 72.24 S1 aspherical 7.3503 0.3997 1.77 47.17 -1.89 S2 aspherical 1.2348 0.5237 S3 spherical endless 4.2000 2.0 24.44 S4 spherical endless 0.3000 STO spherical endless 0.0300 1.92 18.89 5.87 S5 spherical -500.0000 0.7356 S6 spherical -5.4928 0.5200 S7 spherical 4.8598 1.4481 1.59 68.35 4.34 S8 spherical -4.8598 1.2213 1.84 23.78 -2.28 S9 spherical 4.8598 0.1240 S10 aspherical 3.4764 1.5746 1.49 82.51 3.07 S11 aspherical -2.3067 3.0003 S12 spherical endless 3.3000 1.76 52.34 S13 spherical endless 0.3000 1.52 64.21 S14 spherical endless 0.0450 S0 endless

[0134] The conic coefficients and higher-order coefficients A4, A6, A8 and A10 satisfied by the aspherical surface shape in the endoscope are shown in Table 8.

[0135] Table 8

[0136]

[0137] Figure 23 The on-axis chromatic aberration curve of the endoscope is shown. Figure 24 The relative illumination curve of the endoscope is shown. Figure 25 The modulation transfer function curve of the endoscope is shown. Figure 26 The astigmatism curve of the endoscope is shown. Figure 27 The distortion curve of the endoscope is shown. The relative illumination (RI) of the endoscope is greater than 0.8, and the MTFS and MTFT within the 0.7 field of view are both good at 160 lp / mm. In addition, it has good resistance to distortion and chromatic aberration.

[0138] For example, the first prism P3 and the second lens P4 of the endoscope are detachably connected, and the first lens P2 and the second lens P4 are also detachably connected. Specifically, the first lens P2 and the second lens P4 are indirectly connected through the first prism P3.

[0139] Figure 28Another endoscope according to an embodiment of this disclosure is shown. The endoscope includes a protective glass P1, a first lens P2, a first prism P3, a second lens P4, a third lens P5, a fourth lens P6, a fifth lens P7, a third prism P8, and a filter P9. The imaging optical axis is perpendicular to the imaging plane S0. The protective glass P1 to the filter P9 are arranged sequentially along the imaging optical axis from the object side to the image side.

[0140] The first lens P2 may have negative refractive power, and its material may be glass. The object-side surface S1 of the first lens may be convex, and the image-side surface S2 of the first lens may be concave. The mirror surface of the first lens P2 may be aspherical. The second lens P4 may have positive refractive power, and its material may be glass. The object-side surface S5 of the second lens may be concave, and the image-side surface S6 of the second lens may be convex. Specifically, the mirror surface of the second lens P4 may be spherical. The third lens P5 and the fourth lens P6 are cemented together to form a cemented doublet spherical lens. Specifically, the third lens P5 may have positive refractive power, and its material may be glass. The object-side surface S7 of the third lens may be convex. The fourth lens P6 may have negative refractive power, and its material may be glass. The image-side surface S9 of the fourth lens may be concave. The object-side surface S7 of the third lens, the cemented surface S8, and the image-side surface S9 of the fourth lens may all be spherical. The fifth lens P7 may have positive refractive power, and its material may be glass. The object side S10 of the fifth lens may be convex, and the image side S11 of the fifth lens may be convex. Specifically, the mirror surface of the fifth lens P7 is aspherical.

[0141] The first prism P3 is used to transmit light passing through the first lens P2 to the second lens P4. The first prism P3 includes an incident surface S3 and an exit surface S4, which can be perpendicular to the imaging optical axis. The third prism P8 can be made of glass. The object-side surface S12 of the third prism can be flat, and the image-side surface S13 of the third prism can be flat and attached to the filter P9. The image-side surface S14 of the filter can be flat. The aperture stop S0 can be located between the first prism P3 and the second lens P4. Light incident from the protective glass P1 can pass sequentially through the object-side surface S1 of the first lens to the image-side surface S14 of the filter, and then form an image on the imaging plane S0.

[0142] Figure 28 The endoscopic lens shown has a field of view (FOV) of 84° and a total effective focal length (f) of 1.74. Table 9 below shows the parameters of this endoscopic lens, where the units for radius of curvature, distance, and effective focal length are mm.

[0143] Table 9

[0144] Face number Surface type radius of curvature distance Refractive index Abbe number Effective focal length P1 object side spherical endless 0.5500 1.77 72.24 S1 aspherical -66.5728 0.3993 1.77 47.17 -1.61 S2 aspherical 1.3306 0.5589 S3 spherical endless 4.2000 2.0 24.44 S4 spherical endless 0.0300 STO spherical endless 0.3000 1.92 18.89 5.15 S5 spherical -14.7538 0.9363 S6 spherical -3.7747 0.7764 S7 spherical 4.2670 1.1214 1.59 68.35 3.78 S8 spherical -4.2670 0.5630 1.84 23.78 -2.06 S9 spherical 4.2670 0.1134 S10 aspherical 2.7341 2.6699 1.49 82.51 3.39 S11 aspherical -2.9776 3.0014 S12 spherical endless 3.3000 1.76 52.34 S13 spherical endless 0.3000 1.52 64.21 S14 spherical endless 0.0450 S0 endless

[0145] The conic coefficients and higher-order coefficients A4, A6, A8 and A10 satisfied by the aspherical surface shape in the endoscope are shown in Table 10.

[0146] Table 10

[0147]

[0148] Figure 29 The on-axis chromatic aberration curve of the endoscope is shown. Figure 30 The relative illumination curve of the endoscope is shown. Figure 31 The modulation transfer function curve of the endoscope is shown. Figure 32 The astigmatism curve of the endoscope is shown. Figure 33 The distortion curve of the endoscope is shown. The relative illumination (RI) of the endoscope is greater than 0.8, and the MTFS and MTFT within the 0.7 field of view are both good at 160 lp / mm. In addition, it has good resistance to distortion and chromatic aberration.

[0149] For example, the first prism P3 and the second lens P4 of the endoscope are detachably connected, and the first lens P2 and the second lens P4 are also detachably connected. Specifically, the first lens P2 and the second lens P4 are indirectly connected through the first prism P3.

[0150] This disclosure also provides an endoscopic imaging system, including an endoscope lens and an imaging chip disposed on an imaging surface. The endoscope lens may be any of the aforementioned endoscope lenses. The imaging chip may include a complementary metal-oxide-semiconductor (CMOS) or charge-coupled device (CCD) for converting light transmitted from the endoscope lens into electrical signals.

[0151] An endoscope may include, in sequence from the object side to the image side, a first lens, a first prism, a second lens, a third lens, a fourth lens cemented to the third lens, and a fifth lens. The first lens is a glass aspherical negative lens, with its object side being convex or concave and its image side being concave. The second lens is a glass spherical positive lens, with its object side being convex, concave, or flat, and its image side being convex. The third lens is a glass spherical positive lens, with its object side being convex and its image side being a convex surface bonded to the fourth lens. The fourth lens is a glass spherical negative lens, with its object side being a concave surface bonded to the third lens and its image side being concave. The fifth lens is a glass aspherical positive lens, with both its object and image sides being convex.

[0152] For example, the first prism is detachably connected to the second lens, and the first lens can be glued to the first prism.

[0153] In some embodiments, the effective focal length f1 of the first lens satisfies: -2.3 mm < f1 < -1.5 mm, and further may satisfy: -2.1 mm < f1 < -1.6 mm. The effective focal length f2 of the second lens satisfies: 5.0 mm < f2 < 6.5 mm. Exemplarily, the field of view FOV of the endoscope lens satisfies: FOV ≥ 80°. Exemplarily, the absolute value of the distortion of the endoscope lens in the direction of the imaging face diagonal is less than 6%.

[0154] In some embodiments, the effective focal length f3 of the third lens satisfies: 3.5 mm < f3 < 20.0 mm, and further may satisfy 3.7 mm < f3 < 17.4 mm. The effective focal length f4 of the fourth lens satisfies: -30.0 mm < f4 < 0 mm, and further may satisfy: -28.0 mm < f4 < -2.0 mm. Exemplarily, the relative illumination RI of the peripheral field of view of the endoscope lens satisfies: RI > 80%.

[0155] In some embodiments, the optical path length t12 from the image side of the first lens to the object side of the second lens satisfies: 4 mm < t12 < 5 mm, and further may satisfy: 4.4 mm < t12 < 4.6 mm. The maximum diameter of each of the first lens to the fifth lens and the first prism is less than 3.2 mm, where the maximum diameter of the first prism refers to the maximum diagonal length of its cross-sectional projection on the optical axis of the second lens. The first lens to the fifth lens refer to the maximum diameter of the whole relative to its own axis.

[0156] In some embodiments, the effective focal length f5 of the fifth lens satisfies: < 2.5 mm < f5 < 5 mm, and further may satisfy: 3.0 mm < f5 < 4.7 mm. Exemplarily, the total effective focal length f of the endoscope lens satisfies: f < < 1.9 mm. The object distance range when the endoscope imaging system is working can be between 20 mm and 200 mm.

[0157] Exemplarily, the first prism includes a turning prism for turning the optical path. The outgoing light direction of the turning prism is adapted to correspond to the optical axis of the second lens, and the incoming light direction is adapted to correspond to the optical axis of the first lens. The endoscope imaging system may further include a protective glass on the object side of the first lens.

[0158] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered within the scope described in this specification.

[0159] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An endoscope head, characterized by, It includes a first lens, a first prism, a second lens, a third lens, a fourth lens cemented to the third lens, and a fifth lens arranged sequentially from the object side to the image side. The first lens is a glass aspherical negative lens, the image-side surface of the first lens is concave, and the effective focal length f1 of the first lens satisfies: -2.3mm. <f1<-1.5mm; The second lens has positive refractive power, its image-side surface is convex, and its effective focal length f2 satisfies 5.0 mm. <f2<6.5mm; The third lens has positive refractive power, and the object-side surface of the third lens is convex. The fourth lens has a negative refractive force, and the image-side surface of the fourth lens is concave. The fifth lens is a glass aspherical positive lens, with both the object-side and image-side surfaces of the fifth lens being convex.

2. The endoscope head of claim 1, wherein, The first prism is detachably connected to the second lens, and the first lens is detachably connected to the second lens.

3. The endoscope head of claim 2, wherein, The endoscope also includes a second prism, the second prism having a different angle of rotation about the optical axis than the first prism having a different angle of rotation about the optical axis. The second prism is interchangeable with the first prism.

4. The endoscope head of claim 1, wherein, The second lens is a glass aspherical lens or a glass spherical lens, the third lens is a glass aspherical lens or a glass spherical lens, and the fourth lens is a glass aspherical lens or a glass spherical lens.

5. The endoscope head of claim 1, wherein, The object-side surface of the first lens is either convex or concave.

6. The endoscope head of claim 1, wherein, The object-side surface of the second lens is convex, flat, or concave.

7. The endoscope head of claim 1, wherein, The field of view (FOV) of the endoscopic lens satisfies: FOV ≥ 80°.

8. The endoscope head of claim 1, wherein, The absolute value of the distortion of the endoscope in the diagonal direction of the imaging surface is less than 6%.

9. The endoscope head of claim 1, wherein, The effective focal length f3 of the third lens satisfies: 3.5mm <f3<20.0mm; The effective focal length f4 of the fourth lens satisfies: -30.0mm <f4<0mm。 10. The endoscope according to claim 1, wherein, The relative illumination RI of the edge field of view of the endoscope lens satisfies: RI>80%.

11. The endoscope according to claim 1, wherein, The optical path t12 from the image side of the first lens to the object side of the second lens satisfies: 4mm <t12<5mm。 12. The endoscope according to claim 1, wherein, The maximum diameter of each of the first lens to the fifth lens and the first prism is less than 3.2 mm.

13. The endoscope according to claim 1, wherein, The total effective focal length f of the endoscope lens satisfies: f < 1.9 mm.

14. The endoscope according to any one of claims 1 to 13, wherein, The first prism includes a steering prism, the light output direction of which is adapted to correspond to the optical axis of the second lens, and the light input direction of which is adapted to correspond to the optical axis of the first lens. The light-emitting direction of the steering prism intersects with the light-incident direction.

15. The endoscope according to claim 14, wherein, The steering prism includes: The surface exposed to light; The first functional layer is used to transmit light incident through the light-incident surface; A second functional layer is configured to reflect light transmitted through the first functional layer back to the first functional layer, wherein the first functional layer is further configured to reflect light reflected by the second functional layer; and The light-emitting surface is used to transmit light reflected from the first functional layer.

16. The endoscope according to claim 15, wherein, The endoscope also includes a quarter-wave plate located between the first functional layer and the second functional layer; and The first functional layer includes a polarizing beam splitter.

17. An endoscopic imaging system, characterized in that, include: Endoscopic lens as described in any one of claims 1 to 16; as well as An imaging chip is located on the imaging surface of the endoscope lens.

18. The endoscopic imaging system of claim 17 further includes a protective glass located on the object side of the first lens.

Images