Endoscope objective lens

Abstract

The invention provides an endoscope objective lens, and relates to the technical field of medical instruments. Comprising a first spherical lens with negative focal power, a second spherical lens with positive focal power, a third spherical lens with negative focal power, a fourth spherical lens with positive focal power, a fifth spherical lens with positive focal power, an optical filter and protective glass which are sequentially arranged from an object side to an image side. The incident face, facing the object side, of the first spherical lens comprises a plurality of different film coating areas, the film coating areas are provided with different filter films, and the field angles of the multiple film coating areas are different. By setting the form, focal power and related parameters of each spherical lens, the endoscope objective lens has the advantages of large field angle, miniaturization and large depth of field, and by partition coating, changes of a transmittance curve and a reflectivity curve caused by changes of an incident field angle are reduced, light of a laser band is cut off, and the anti-laser effect of a coating film is ensured; under the laser-free working condition, color cast during large-field-angle imaging is avoided, and the image quality is improved.

Description

Technical Field

[0001] The present application relates to the technical field of medical devices, and in particular to an endoscope objective lens. Background Art

[0002] In the medical field, endoscopes are used as inspection and treatment equipment to help doctors effectively determine the lesion area and degree of lesions in the body cavity. With the development and progress of science and technology, the requirements for endoscopes are getting higher and higher. For example, endoscopes are required to have a larger field of view or higher optical resolution to be able to observe the lesion area more carefully and accurately, so as to determine whether the lesion is benign or malignant.

[0003] In addition, laser technology also plays an important role in endoscopic diagnosis and treatment. Endoscopic laser therapy is an advanced medical method that combines endoscopic technology and laser technology and is widely used in the diagnosis and treatment of various diseases. Endoscopic laser therapy uses the high energy and precise focusing characteristics of lasers to directly transmit the laser to the lesion through the endoscope to achieve precise treatment of the lesion tissue.

[0004] Existing endoscope objective systems face technical challenges in achieving a large field of view, miniaturization, and a large depth of field. For example, an ultra-large field of view is effective for endoscopic clinical practice, especially for colonoscopy to observe the lateral folds of the intestinal wall, and has important application value. However, existing technologies are difficult to ensure high-definition functions while achieving an ultra-large field of view. In addition, when an endoscope is combined with a laser for treatment, when the laser (wavelength 980nm or wavelength 1064nm, etc.) is incident on the camera element, it will cause a halo in the endoscopic image, affecting the image quality. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide an endoscope objective lens having the functions of a large field of view, a large depth of field and high-quality images.

[0006] According to one aspect of an embodiment of the present application, an endoscope objective lens is provided, comprising: a first spherical lens with negative optical focal length, a second spherical lens with positive optical focal length, a third spherical lens with negative optical focal length, a fourth spherical lens with positive optical focal length, a fifth spherical lens with positive optical focal length, a filter and a protective glass, which are arranged in sequence from the object side to the image side; the incident surface of the first spherical lens facing the object side comprises a plurality of different coating areas, the coating areas have different filter films, and the plurality of coating areas have different field of view angles.

[0007] Optionally, the number of the coating areas is three, and the viewing angles of the three coating areas are respectively 0-85°, 85°-130°, and ≥130°.

[0008] Optionally, an aperture is further arranged between the second spherical lens and the third spherical lens, and the aperture is symmetrical along the optical axis.

[0009] Optionally, the refractive index of the first spherical lens is 1.7<Nd1<1.9, and the Abbe number is 70<Vd1<80;

[0010] The refractive index of the second spherical lens is 1.8<Nd2<2.0, and the Abbe number is 30<Vd2<40;

[0011] The refractive index of the third spherical lens is 1.8<Nd3<2.0, and the Abbe number is 20<Vd3<30;

[0012] The refractive index of the fourth spherical lens is 1.4<Nd4<1.6, and the Abbe number is 60<Vd4<85;

[0013] The refractive index of the fifth spherical lens is 1.8<Nd5<2.0, and the Abbe number is 10<Vd5<25.

[0014] Optionally, the endoscope objective lens satisfies: 0.9<|f / f1|<1.0, 0.4<|f / f2|<0.5, 0.2<|f / f3|<0.3, 0.5<|f / f4|<0.6, 0.7<|f / f5|<0.8; f is the effective focal length of the endoscope objective lens, f1 is the focal length of the first spherical lens, f2 is the focal length of the second spherical lens, f3 is the focal length of the third spherical lens, f4 is the focal length of the fourth spherical lens, and f5 is the focal length of the fifth spherical lens.

[0015] Optionally, the fourth spherical lens and the fifth spherical lens are glued together, the image side surface of the fourth spherical lens is a convex surface, the object side surface of the fifth spherical lens is a concave surface, and the fourth spherical lens and the fifth spherical lens are glued together via the convex surface and the concave surface.

[0016] Optionally, the endoscope objective lens satisfies: 2<|f2 / f1|<2.2, 0<|f3 / f45|<0.2, 0.1<f / (f1+f2+f3+f4+f5)<0.3, 0<f / (f1+f2+f45)<0.1; f45 is the combined focal length of the fourth spherical lens and the fifth spherical lens.

[0017] Optionally, the endoscope objective lens satisfies: |D2 / R2|≤1.8; wherein D2 represents the aperture of the exit surface of the first spherical lens, and R2 represents the radius of curvature of the exit surface of the first spherical lens.

[0018] Optionally, the endoscope objective lens satisfies: 2.5≤TTL / (d1+d2+d3)≤4; wherein d1 represents the thickness of the first spherical lens, d2 represents the thickness of the second spherical lens, d3 represents the thickness of the third spherical lens, and TTL represents the total length of the endoscope objective lens.

[0019] Optionally, the effective focal length f of the endoscope objective lens is 0.8-1.0 mm, the ratio of the effective focal length to the entrance pupil diameter FNO≤6, the total length TTL≤6.0 of the endoscope objective lens, and the maximum optical aperture of the endoscope objective lens≤2.2.

[0020] The endoscope objective lens provided in an embodiment of the present application includes: a first spherical lens with negative optical focal length, a second spherical lens with positive optical focal length, a third spherical lens with negative optical focal length, a fourth spherical lens with positive optical focal length, a fifth spherical lens with positive optical focal length, a filter and a protective glass, which are arranged in sequence from the object side to the image side; the incident surface of the first spherical lens facing the object side includes multiple different coating areas, the coating areas have different filter films, and the multiple coating areas have different field of view angles.

[0021] By rationally controlling the shape, focal length and related parameter relationships of each spherical lens, the endoscope objective lens of the present application can well correct chromatic aberration, astigmatism, coma and field curvature, so that the endoscope objective lens has the advantages of large field of view, miniaturization and large depth of field, so as to meet the demand for high-performance endoscope objective lenses in the medical field. A plurality of coating areas with different field of view angles are arranged on the incident surface of the first spherical lens to realize zoned coating, which can reduce the changes in the transmittance curve and reflectivity curve caused by the change of the incident field of view angle, and then cut off the light in the laser band to ensure the anti-laser effect of the coating; and in the absence of laser working conditions, the color deviation during imaging with a large field of view angle is eliminated to improve the image quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 is a schematic diagram of the structure of the endoscope objective lens provided in this embodiment;

[0024] Figure 2 is a distribution diagram of the coating area on the incident surface of the first spherical lens of the endoscope objective provided by this embodiment;

[0025] Figure 3is an MTF curve diagram of the endoscope objective lens provided in this embodiment under visible light;

[0026] Figure 4 is a vertical axis chromatic aberration diagram of the endoscope objective lens provided in this embodiment under visible light;

[0027] Figure 5 3 is a vertical axis chromatic aberration curve of the endoscope objective lens provided in this embodiment under visible light.

[0028] Icon: 1-first spherical lens; 1a-first coating area; 1b-second coating area; 1c-third coating area; 2-second spherical lens; 3-third spherical lens; 4-fourth spherical lens; 5-fifth spherical lens; 6-protective glass; 7-aperture. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0030] In the description of this application, it should be noted that the terms "inside", "outside", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed when in use, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0031] It should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0032] When an endoscope is used in conjunction with a laser, the laser will cause a halo in the endoscopic image when it is incident on the imaging element. In order to prevent such a halo in the endoscopic image, it is necessary to add a filter film to the optical system. The function of the filter film is to cut off the wavelength range of the laser that produces the halo.

[0033] However, endoscopes generally require a larger field of view, especially gastroscopes; when using reflective filters, as the incident field of view increases, the working wavelength of the filter will move toward the short-wave direction. This is because the change in the incident field of view causes the optical path of the light in the film to change, thereby affecting the interference conditions of the film, causing the spectral characteristics at the originally designed specific wavelength to shift.

[0034] Moreover, changes in the incident viewing angle will change the transmittance curve and reflectance curve. Generally, when the incident viewing angle increases, the transition zone between the cutoff point and the high transmittance point of the filter film will become wider or narrower, and the transmittance and cutoff depth (OD value) will also decrease accordingly; the increase in the incident viewing angle will lead to a decrease in the reflectivity of the wavelength range that requires high reflection.

[0035] In view of this, please refer to Figure 1 As shown, an embodiment of the present application provides an endoscope objective lens, comprising: a first spherical lens 1 with negative optical focal length, a second spherical lens 2 with positive optical focal length, a third spherical lens 3 with negative optical focal length, a fourth spherical lens 4 with positive optical focal length, a fifth spherical lens 5 with positive optical focal length, a filter (not shown in the figure) and a protective glass 6, which are arranged in sequence from the object side to the image side; the incident surface of the first spherical lens 1 facing the object side includes multiple different coating areas, the coating areas have different filter films, and the different filter films can be obtained by coating film layers of different thicknesses and different materials, etc. The field of view angles of the multiple coating areas are different, and the field of view angle here is the incident field of view angle.

[0036] The first spherical lens 1, the second spherical lens 2, the third spherical lens 3, the fourth spherical lens 4, the fifth spherical lens 5, the filter and the protective glass 6 are sequentially arranged along the optical axis, and the incident light passes through the above components sequentially.

[0037] Furthermore, the incident surface of the first spherical lens 1 of the present application is divided into a plurality of different coating areas. Figure 2 In the example, the incident surface of the first spherical lens 1 is divided into three coating areas, the viewing angle of the first coating area 1a is 0-85°, the viewing angle of the second coating area 1b is 85°-130°, and the viewing angle of the third coating area 1c is ≥130°.

[0038] Of course, the number of coating areas may also be set to other numbers according to the situation, and the field of view angle of each coating area is not limited to the above-mentioned field of view angle. The specific number is selected according to actual needs and will not be elaborated here.

[0039] The present application reasonably controls the shape, optical focal length and related parameter relationships of each spherical lens, so that the endoscope objective lens of the present application can well correct chromatic aberration, astigmatism, coma and field curvature, so that the endoscope objective lens has the advantages of large field of view, miniaturization and large depth of field, so as to meet the demand for high-performance endoscope objective lenses in the medical field.

[0040] In addition, the present application sets a plurality of coating areas with different field of view angles on the incident surface of the first spherical lens 1, and each coating area has a different filter film, which can reduce the changes in the transmittance curve and the reflectance curve caused by the change of the incident field of view angle, and then cut off the light in the laser band to ensure the anti-laser effect of the coating; and in the absence of laser working conditions, the color deviation during imaging with a large field of view angle is eliminated, thereby improving the image quality.

[0041] In addition, a stop 7 is provided in the middle of the endoscope objective lens. Figure 1 The optical axis direction is bilaterally symmetrical, which is beneficial to correcting the off-axis aberration of the endoscope objective lens. The aperture 7 is located between the second spherical lens 2 and the third spherical lens 3.

[0042] For the specific parameters of each spherical lens, please see the following settings;

[0043] The refractive index of the first spherical lens 1 is 1.7<Nd1<1.9, and the Abbe number is 70<Vd1<80;

[0044] The refractive index of the second spherical lens 2 is 1.8<Nd2<2.0, and the Abbe number is 30<Vd2<40;

[0045] The refractive index of the third spherical lens 3 is 1.8<Nd3<2.0, and the Abbe number is 20<Vd3<30;

[0046] The refractive index of the fourth spherical lens 4 is 1.4<Nd4<1.6, and the Abbe number is 60<Vd4<85;

[0047] The refractive index of the fifth spherical lens 5 is 1.8<Nd5<2.0, and the Abbe number is 10<Vd5<25.

[0048] The endoscope objective lens satisfies: 0.9<|f / f1|<1.0, 0.4<|f / f2|<0.5, 0.2<|f / f3|<0.3, 0.5<|f / f4|<0.6, 0.7<|f / f5|<0.8; f is the effective focal length of the endoscope objective lens, f1 is the focal length of the first spherical lens 1, f2 is the focal length of the second spherical lens 2, f3 is the focal length of the third spherical lens 3, f4 is the focal length of the fourth spherical lens 4, and f5 is the focal length of the fifth spherical lens 5.

[0049] Further, the fourth spherical lens 4 and the fifth spherical lens 5 are glued together, the image side surface of the fourth spherical lens 4 is a convex surface, the object side surface of the fifth spherical lens 5 is a concave surface, and the fourth spherical lens 4 and the fifth spherical lens 5 are glued together through the convex surface and the concave surface.

[0050] The endoscope objective lens also satisfies: 2<|f2 / f1|<2.2, 0<|f3 / f45|<0.2, 0.1<f / (f1+f2+f3+f4+f5)<0.3, 0<f / (f1+f2+f45)<0.1; f45 is the combined focal length of the fourth spherical lens 4 and the fifth spherical lens 5.

[0051] The endoscope objective lens also satisfies: |D2 / R2|≤1.8; wherein D2 represents the aperture of the exit surface of the first spherical lens 1 , and R2 represents the radius of curvature of the exit surface of the first spherical lens 1 .

[0052] The endoscope objective lens also satisfies: 2.5≤TTL / (d1+d2+d3)≤4;

[0053] Wherein, d1 represents the thickness of the first spherical lens 1 , d2 represents the thickness of the second spherical lens 2 , d3 represents the thickness of the third spherical lens 3 , and TTL represents the total length of the endoscope objective lens.

[0054] In the embodiment of the present application, the effective focal length f of the endoscope objective is 0.8-1.0 mm, the ratio of the effective focal length to the entrance pupil diameter FNO≤6, TTL≤6.0, and the maximum optical aperture ≤2.2.

[0055] Through the above-mentioned configuration, the endoscope objective lens provided in the embodiment of the present application has an optical system with a full field angle of ≥170° and a designed depth of field range of 3mm to 100mm.

[0056] Table 1 below lists the parameters of each component:

[0057] Table 1

[0058]

[0059] Figure 3 This is the MTF curve of the endoscope objective lens under visible light. Figure 3 It can be seen that when the spatial frequency of the endoscope objective is 220l p / mm, the full-field MTF value is greater than 0.1, the imaging quality is excellent, and the resolution of the lens is high.

[0060] Figure 4 This is the vertical axis chromatic aberration diagram of the endoscope objective under visible light. Figure 5 The vertical axis chromatic aberration curve of the endoscope objective lens under visible light is shown in Figure 2. Figure 5It can be seen that the vertical axis chromatic aberration is less than 1um, the chromatic aberration is small, and the image color reproduction is high.

[0061] The above are only embodiments of the present application and are not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. An endoscope objective lens, characterized in that: include: A first spherical lens with negative optical power, a second spherical lens with positive optical power, a third spherical lens with negative optical power, a fourth spherical lens with positive optical power, a fifth spherical lens with positive optical power, a filter and a protective glass are arranged in sequence from the object side to the image side; the incident surface of the first spherical lens facing the object side includes a plurality of different coating areas, the coating areas have different filter films, and the plurality of coating areas have different field of view angles.

2. The endoscope objective lens according to claim 1, characterized in that: The number of the coating areas is three, and the viewing angles of the three coating areas are respectively 0-85°, 85°-130°, and ≥130°.

3. The endoscope objective lens according to claim 1, characterized in that: An aperture is further arranged between the second spherical lens and the third spherical lens, and the aperture is symmetrical along the optical axis.

4. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The refractive index of the first spherical lens is 1.7<Nd1<1.9, and the Abbe number is 70<Vd1<80; The refractive index of the second spherical lens is 1.8<Nd2<2.0, and the Abbe number is 30<Vd2<40; The refractive index of the third spherical lens is 1.8<Nd3<2.0, and the Abbe number is 20<Vd3<30; The refractive index of the fourth spherical lens is 1.4<Nd4<1.6, and the Abbe number is 60<Vd4<85; The refractive index of the fifth spherical lens is 1.8<Nd5<2.0, and the Abbe number is 10<Vd5<25.

5. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The endoscope objective lens satisfies: 0.9<|f / f1|<1.0, 0.4<|f / f2|<0.5, 0.2<|f / f3|<0.3, 0.5<|f / f4|<0.6, 0.7<|f / f5|<0.8; f is the effective focal length of the endoscope objective lens, f1 is the focal length of the first spherical lens, f2 is the focal length of the second spherical lens, f3 is the focal length of the third spherical lens, f4 is the focal length of the fourth spherical lens, and f5 is the focal length of the fifth spherical lens.

6. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The fourth spherical lens and the fifth spherical lens are glued together, the image side surface of the fourth spherical lens is a convex surface, the object side surface of the fifth spherical lens is a concave surface, and the fourth spherical lens and the fifth spherical lens are glued together through the convex surface and the concave surface.

7. The endoscope objective lens according to claim 6, characterized in that: The endoscope objective lens satisfies: 2<|f2 / f1|<2.2, 0<|f3 / f45|<0.2, 0.1<f / (f1+f2+f3+f4+f5)<0.3, 0<f / (f1+f2+f45)<0.1; f45 is the combined focal length of the fourth spherical lens and the fifth spherical lens.

8. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The endoscope objective lens satisfies: |D2 / R2|≤1.8; wherein D2 represents the aperture of the exit surface of the first spherical lens, and R2 represents the radius of curvature of the exit surface of the first spherical lens.

9. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The endoscope objective lens satisfies: 2.5≤TTL / (d1+d2+d3)≤4; wherein d1 represents the thickness of the first spherical lens, d2 represents the thickness of the second spherical lens, d3 represents the thickness of the third spherical lens, and TTL represents the total length of the endoscope objective lens.

10. The endoscope objective lens according to any one of claims 1 to 3, characterized in that: The effective focal length f of the endoscope objective lens is 0.8-1.0 mm, the ratio of the effective focal length to the entrance pupil diameter FNO≤6, the total length TTL≤6.0 of the endoscope objective lens, and the maximum optical aperture of the endoscope objective lens≤2.2.

Images