An endoscope optical system

Abstract

The present invention discloses an endoscope optical system, which consists of a first lens, a turning prism, an aperture, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a dichroic prism from the object plane to the image plane. The first lens has a negative optical power, a convex object side and a concave image side; the second lens has a positive optical power, a flat object side and a convex image side; the object side of the third lens is a convex surface, the optical power of the fourth lens is opposite to that of the third lens, and the image side is a convex surface; the fifth lens has a positive optical power and a convex image side; the sixth lens has a negative optical power, a concave object side and a concave image side; the seventh lens has a positive optical power, a convex object side and a convex image side; the object-side numerical aperture NA of the endoscope optical system satisfies the following: 0.001<NA<0.006. The advantage of the endoscope optical system is that a combination of lenses with different surface shapes and optical powers is used to reduce the object-side numerical aperture, thereby improving the depth of field and axial resolution capability of the endoscope.

Description

Technical Field

[0001] The present invention relates to an optical system, in particular to an endoscope optical system. Background Art

[0002] Endoscopes are widely used in the medical field. With the development of medical equipment and related technologies, performance requirements for endoscopes have also increased. Once an endoscope enters the human body, it needs to image tissues within a large working range. Chinese utility model patent publication number CN218383456U provides an endoscope objective zoom optical system. This system uses a movable lens assembly to adapt to objects at varying distances while maintaining good image quality. However, the presence of this movable mechanism reduces the reliability and service life of the endoscope and increases manufacturing costs.

[0003] To improve the comprehensiveness and accuracy of diagnosis, endoscopes are equipped with steering prisms and beam splitters, providing doctors with a more convenient user experience. These prisms are typically composed of multiple prisms, where light is reflected multiple times before being deflected. This not only changes the beam transmission angle, but also allows for the generation of images with a variety of different properties—such as white light, fluorescence, and polarized light—to improve the accuracy of the final image. This impacts light energy utilization and places high precision requirements on the prism angles. US Patent No. US11805983B2 proposes a light path deflection prism that achieves light path deflection through a combination of shaped prisms and a mirror coating, improving light transmittance. However, the shaped prisms increase manufacturing costs and assembly difficulty. Chinese Patent Application Publication No. CN114176485A uses a beam splitter to generate white light and polarized light, providing clearer images in blurry environments. However, to ensure that the images of the various beams coordinate well, the beam splitter is lengthened to compensate for the optical path, resulting in a larger rear-end lens volume and hindering practical use. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an endoscope optical system capable of improving the depth of field and axial resolution capability.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: an endoscope optical system, which is composed of a first lens, a turning prism, an aperture, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a dichroic prism from the object plane to the image plane, wherein the optical focal length of the first lens is negative, the object side is convex, and the image side is concave; the optical focal length of the second lens is positive, the object side is flat, and the image side is convex; the object side of the third lens is convex, the optical focal length of the fourth lens is opposite to that of the third lens, and the image side is convex; the optical focal length of the fifth lens is positive, and the image side is convex; the optical focal length of the sixth lens is negative, the object side is concave, and the image side is concave; the optical focal length of the seventh lens is positive, and the object side is convex, and the image side is convex; the object-side numerical aperture NA of the endoscope optical system satisfies the following: 0.001<NA<0.006.

[0006] Compared with the existing technology, the advantages of the present invention are that it uses a combination of lenses with different surface shapes and optical focal lengths, and by reducing the object-side numerical aperture, it improves the depth of field and axial resolution of the endoscope. At the same time, it uses a turning prism and a beam splitter prism to realize the steering and beam splitting functions of the full field of view, thereby improving the utilization rate of light energy. By imaging light beams of various properties such as white light, fluorescence, and polarized light, the imaging performance of the endoscope is improved while maintaining a small volume.

[0007] Preferably, both surfaces of the first lens are aspherical. Selecting aspherical surfaces can further improve the imaging quality of the lens and reduce aberrations in the imaging system.

[0008] Preferably, the third lens and the fourth lens form a doublet, and the fifth lens, the sixth lens, and the seventh lens form a triplet. Doublets and triplet lenses can balance chromatic aberration during the propagation of broad-spectrum light, correct on-axis and off-axis chromatic aberration and aberration, and reduce lens sensitivity.

[0009] Preferably, the focal length f of the endoscope optical system and the focal length f of the first lens are L1 The focal length of the second lens is f L2 The focal length f of the doublet lens 34 The focal length f of the triplet lens 567 Satisfy respectively: -0.8<f L1 / f<-0.7,1.5<f L2 / f<1.7,3.2<f 34 / f<3.5,-900000<f 567 / f<-9000. The focal length of the triplet lens is large, close to that of flat glass, which can maintain the image height and adjust the angle of light.

[0010] Preferably, the refractive index of the material of the first lens is defined as Nd L1 The refractive index of the second lens is Nd L2 The refractive index of the third lens is Nd L3 The refractive index of the fourth lens is Nd L4 The refractive index of the material of the fifth lens is Nd L5 The refractive index of the sixth lens is Nd L6 The refractive index of the seventh lens is Nd L7 , respectively satisfying: 1.9<Nd L1 <2.1,1.6<Nd L2 <1.8,0.15<|Nd L3 -Nd L4 |<0.25,0.15<|Nd L5 -Nd L6 |<0.25,0.15<|Nd L6 -Nd L7 |<0.25.

[0011] Preferably, the steering prism is provided with a steering incident surface, a first reflection surface, a second reflection surface and a steering exit surface. The steering exit surface is located between the first reflection surface and the second reflection surface and is perpendicular to the optical axis of the endoscope optical system. The light is vertically incident on the steering incident surface and is incident on the first reflection surface at a first incident angle, is reflected by the first reflection surface and is incident on the second reflection surface at a second incident angle, and is then reflected by the second reflection surface to the steering exit surface and then exits vertically. The steering angle of the steering prism is defined as θ, the angle between the steering incident surface and the second reflection surface is θ1, the angle between the second reflection surface and the first reflection surface is θ2, and the angle between the first reflection surface and the optical axis of the endoscope optical system is θ3, which respectively satisfy the following relationships: θ=30°, θ2=θ / 2, θ1+θ2+θ3+θ=90°, 6°<θ3<16°. By adjusting the shape of the steering prism to achieve a 30° light steering function and controlling the degree of light deflection inside the steering prism, it is possible to avoid light energy loss caused by light exiting the steering prism and at the same time control the volume of the steering prism.

[0012] Preferably, the turning prism is a single prism, and the angle θ3 between the first reflective surface and the optical axis of the endoscope optical system is 15°. Controlling the turning length of light in the turning prism and coordinating it with the field of view of the optical system ensures that the optical path difference between the edge field of view and the center field of view in the turning prism is small and symmetrical, minimizing the impact on imaging quality.

[0013] Preferably, the steering prism is composed of a first sub-prism and a second sub-prism glued together, the steering incident surface is the object side surface of the first sub-prism, the first reflection surface is in contact with the air, the second reflection surface is the glued surface of the first sub-prism and the second sub-prism, the steering exit surface is the image side surface of the second sub-prism, and the angle θ3=7° or θ3=10° between the first reflection surface and the optical axis of the endoscope optical system.

[0014] Preferably, the first reflective surface is coated with a reflective film, and the refractive index of the first sub-prism is defined as Nd G01 The refractive index of the second sub-prism is Nd G02 , the second incident angle is θ5, satisfying: Nd G01 ≤Nd G02 *sinθ5. The reflective function of the first reflective surface is achieved by coating with a reflective film, while the reflective function of the second reflective surface is achieved by the difference in refractive index between the first sub-prism and the second sub-prism. This allows light to be fully reflected by the second reflective surface, thus reducing coating costs.

[0015] Preferably, the refractive index of the first sub-prism is defined as Nd G01 The refractive index of the second sub-prism is Nd G02 , the second incident angle is θ5, satisfying: Nd G01 ≤Nd G02 *sin(θ5-8°). This structure not only reduces coating costs, but also allows the entire field of view to be fully reflected by the second reflective surface, reducing light energy loss.

[0016] Preferably, the dichroic prism is formed by gluing together multiple dichroic prisms made of the same material, and the gluing surfaces of each dichroic prism are dichroic surfaces. The light emitted from the seventh lens is incident from the dichroic incident surface of the dichroic prism, is split into light of different properties on different dichroic surfaces, and then is emitted from the dichroic exit surfaces of different dichroic prisms in the dichroic prism.

[0017] Preferably, the dichroic prism is formed by gluing together a first dichroic prism, a second dichroic prism and a third dichroic prism made of the same material. The object side surface of the first dichroic prism is the dichroic incident surface of the dichroic prism, the gluing surface of the first dichroic prism and the second dichroic prism is the first dichroic surface, the image side surface of the first dichroic prism is defined as the first dichroic exit surface, the gluing surface of the second dichroic prism and the third dichroic prism is defined as the second dichroic exit surface, the image side surface of the second dichroic prism is defined as the second dichroic exit surface, the image side surface of the third dichroic prism is defined as the third dichroic exit surface, and the dichroic incident surface of the dichroic prism is defined as the second dichroic exit surface. The angle between the surface and the first splitting surface is θ61, and the angle between the first splitting surface and the second splitting surface is θ71, which respectively satisfy: 25°<θ61<35°, 35°<θ71<45°; the length of the first section of the light in the first splitting prism is defined as d11, the length of the first section in the second splitting prism is defined as d21, and the length of the first section in the third splitting prism is defined as d31, which respectively satisfy: 0.7mm<d11<0.9mm, 0.9mm<d21<1.1mm, 3.7mm<d11+d21+d31<3.9mm.

[0018] Preferably, the dichroic prism is formed by gluing a first dichroic prism and a second dichroic prism made of the same material, the object side surface of the first dichroic prism is the dichroic incident surface of the dichroic prism, the gluing surface of the first dichroic prism and the second dichroic prism is defined as the first dichroic surface, the image side surface of the first dichroic prism is the first dichroic exit surface, the image side surface of the second dichroic prism is the second dichroic exit surface, the angle between the dichroic incident surface of the dichroic prism and the first dichroic surface is θ62=45°, the length of the first segment of the light in the first dichroic prism is defined as d12, the length of the second segment is defined as d22, and the length of the light in the second dichroic prism is defined as d32, which respectively satisfy the following: 2.1mm<d12<2.3mm, 1.5mm<d22<1.7mm, 1.5mm<d32<1.7mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the endoscope optical system according to the embodiment and example 1 of the present invention;

[0020] Figure 2 This is a schematic structural diagram of the endoscope optical system of the present invention, in which the steering prism is a single prism;

[0021] Figure 3 This is a schematic structural diagram of the endoscope optical system of the present invention, in which the turning prism is a double prism;

[0022] Figure 4 This is a schematic structural diagram of the endoscope optical system of the present invention, in which the turning prism is a triangular prism;

[0023] Figure 5 A schematic structural diagram of the endoscope optical system of the present invention in which the beam splitter prism is a triangular prism;

[0024] Figure 6 A schematic structural diagram of the endoscope optical system of the present invention in which the beam splitter prism is a bi-prism;

[0025] Figure 7 This is a transfer function curve diagram of Example 1 of the present invention at an object distance of 50 mm;

[0026] Figure 8 This is a transfer function curve diagram of Example 1 of the present invention at an object distance of 35 mm;

[0027] Figure 9 This is a transfer function curve diagram of Example 1 of the present invention at an object distance of 125 mm;

[0028] Figure 10 Schematic diagram of the structure of the endoscope optical system of Example 2 of the present invention;

[0029] Figure 11 This is a transfer function curve diagram of Example 2 of the present invention at an object distance of 50 mm;

[0030] Figure 12 This is a transfer function curve diagram of Example 2 of the present invention at an object distance of 35 mm;

[0031] Figure 13 This is a transfer function curve diagram of Example 2 of the present invention at an object distance of 125 mm;

[0032] Figure 14 Schematic diagram of a four-eye endoscope optical system according to Example 1 of the present invention;

[0033] Figure 15 Schematic diagram of the binocular endoscope optical system of Example 1 of the present invention.

[0034] Description of reference numerals:

[0035] L1, first lens; G, turning prism; G01, first sub-prism; G02, second sub-prism; G03, third sub-prism; STO, aperture; L2, second lens; L3, third lens; L4, fourth lens; L5, fifth lens; L6, sixth lens; L7, seventh lens; P, beam splitter; P01, first beam splitter; P02, second beam splitter; P03, third beam splitter; IMA, image plane; IMA1, first image plane; IMA2, second image plane; IMA3, third image plane; GS1, first protective glass; GS2, second protective glass; S1, steering incident surface; S2, first reflection surface; S3, second reflection surface; S4, steering exit surface; S5, beam splitting incident surface;

[0036] Figure 5 Description of reference numerals in the accompanying drawings: S61, first light splitting surface; S71, first light splitting exit surface; S81, second light splitting surface; S91, second light splitting exit surface; S101, third light splitting exit surface;

[0037] Figure 6 Description of the reference numerals in the accompanying drawings: S62, first light splitting surface; S72, first light splitting exit surface; S92, second light splitting exit surface. DETAILED DESCRIPTION

[0038] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0039] The following is a detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, which are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention.

[0040] Example:

[0041] In the drawings, the thickness, size and shape of the lenses have been slightly exaggerated for ease of illustration. The drawings are for schematic purposes only and are not drawn strictly to scale.

[0042] In an exemplary embodiment, to improve the imaging quality of the lens and reduce aberrations in the imaging system, the aspheric lens surface used satisfies the following equation:

[0043] .

[0044] in, y represents the radial coordinate value of the lens perpendicular to the optical axis of the endoscope optical system, The aspheric lens is located at a height of y When the position is , the sagittal height from the vertex of the aspheric surface is, c =1 / R, R represents the curvature radius corresponding to the center of the aspheric lens surface. k represents the cone coefficient, parameter B 、 C are the coefficients of the 4th and 6th order terms of the high-order aspheric polynomial respectively.

[0045] The endoscope optical system operates in the wavelength range of 0.486um~1um, with a central wavelength of 0.587um and fluorescence in the wavelength range of 0.82um~1um.

[0046] An endoscope optical system, such as Figure 1As shown, from the object plane to the image plane IMA is composed of the first lens L1, the turning prism G, the aperture STO, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7 and the dichroic prism P. The first protective glass GS1 and the second protective glass GS2 are respectively provided at both ends of the endoscope optical system for protection.

[0047] Consider placing a filter or applying a filter film layer in the endoscope optical system to filter out stray light. To save costs, one filter can be provided; to increase the cutoff depth and improve image quality, two filters can also be provided. Typically, the filter can be placed between the aperture STO and the third lens L3, or between the fourth lens L4 and the image plane IMA. The filter film layer can be placed on the image side surface of the fourth lens L4, the object side surface of the fifth lens L5, or the object side surface of the dichroic prism P. Typically, the curvature radius of the image side surface of the fourth lens L4 and the curvature radius of the object side surface of the fifth lens L5 are set relatively large, and the object side surface of the dichroic prism P is set to a plane, so that the filtering effect is better when the filter film layer is applied.

[0048] The object-side numerical aperture (NA) of the endoscope optical system satisfies the following conditions: 0.001 < NA < 0.006. The distance between the object plane and the object-side surface of the first lens L1 is the object distance d, which satisfies the following conditions: 30 mm ≤ d ≤ 125 mm, and more preferably, d = 50 mm. Controlling the object-side numerical aperture (NA) of the endoscope optical system within a narrow range can achieve a larger depth of field, improve the axial resolution capability of the endoscope, and provide physicians with more comprehensive and detailed information about internal human tissues.

[0049] The first lens L1 has a negative refractive power, a convex surface on the object side, and a concave surface on the image side. L1 Satisfies: -0.8<f L1 / f<-0.7, defines the refractive index of the material of the first lens L1 as Nd L1 , satisfying: 1.9<Nd L1 <2.1, choosing high refractive index materials can effectively collect light and reduce aberrations.

[0050] The second lens L2 has a positive optical power, a flat object side, and a convex image side. The focal length f of the second lens L2 is L2 Satisfy: 1.5<f L2 / f<1.7, the refractive index of the material of the second lens L2 is defined as Nd L2 , satisfying: 1.6<Nd L2 <1.8, choosing a material with a higher refractive index can effectively converge light and reduce aberrations.

[0051] The object side of the third lens L3 is convex, the optical power of the fourth lens L4 is opposite to that of the third lens L3, and the image side is convex. The third lens L3 and the fourth lens L4 form a doublet lens. The focal length f of the doublet lens formed by the third lens L3 and the fourth lens L4 is 34 Satisfy: 3.2<f 34 / f<3.5, which can converge light and control the imaging height. The refractive index of the material of the third lens L3 is defined as Nd L3 The refractive index of the material of the fourth lens L4 is Nd L4 , satisfying: 0.15<|Nd L3 -Nd L4 |<0.25, the chromatic aberration in the propagation of wide-spectrum light is balanced by a double-cemented lens, which can correct chromatic aberration and aberration on and off the axis and reduce the sensitivity of the lens.

[0052] The fifth lens L5 has a positive focal power and a convex image side surface. The sixth lens L6 has a negative focal power and a concave object side surface and a concave image side surface. The seventh lens L7 has a positive focal power and a convex object side surface and a convex image side surface. The fifth lens L5, the sixth lens L6 and the seventh lens L7 form a triplet lens. The focal length of the triplet lens is f 567 Satisfies: -900000<f 567 / f<-9000, the focal length of the triplet lens is f 567 It is larger, close to flat glass, and can maintain the image height and adjust the angle of light. The refractive index of the material of the fifth lens L5 is defined as Nd L5 The refractive index of the sixth lens L6 is Nd L6 The refractive index of the seventh lens L7 is Nd L7 , respectively satisfying: 0.15<|Nd L5 -Nd L6 |<0.25,0.15<|Nd L6 -Nd L7 |<0.25, the chromatic aberration in the propagation of wide-spectrum light is balanced by a triplet lens, which can correct chromatic aberration and aberration on and off the axis and reduce the sensitivity of the lens.

[0053] The turning prism G may be composed of three sub-prisms or two sub-prisms, or may be a single prism.

[0054] Figure 2 The steering prism G shown is a single prism. Light enters the steering incident surface S1, is reflected sequentially from the first and second reflective surfaces S2 and S3, and finally exits the steering exit surface S4, achieving light redirection. The first and second reflective surfaces S2 and S3 are coated with reflective coatings, allowing the entire field of view of light to be reflected by the steering prism G, thus reducing light energy loss.

[0055] from Figure 2 It can be seen that the steering angle of the steering prism G is θ, the angle between the steering incident surface S1 and the second reflecting surface S3 is θ1, the angle between the second reflecting surface S3 and the first reflecting surface S2 is θ2, the angle between the first reflecting surface S2 and the optical axis of the endoscope optical system is θ3, the incident angle of the light reaching the first reflecting surface S2 is θ4, and the incident angle of the light reaching the second reflecting surface S3 is θ5, satisfying: θ=30°, θ2=θ / 2, θ1+θ2+θ3+θ=90°, 6°<θ3<16°, and the 30° light steering function is achieved by adjusting the shape of the steering prism G, and the degree of deflection of the light inside the steering prism G is controlled to avoid light energy loss caused by light exiting the steering prism G, and the volume of the steering prism G can be controlled at the same time. The best solution is θ3=15°, which controls the turning length of the light in the turning prism G. Combined with the field of view angle of the optical system, it can ensure that the optical path difference between the light in the edge field of view and the central field of view in the turning prism G is small and symmetrical, reducing the impact on image quality.

[0056] Figure 3 The steering prism G shown is composed of a first sub-prism G01 and a second sub-prism G02 glued together. The object side of the first sub-prism G01 is the steering incident surface S1. The contact surface of the second sub-prism G02 with the air is the first reflective surface S2. The reflective function of the first reflective surface S2 is achieved by coating with a reflective film. The contact surface between the first sub-prism G01 and the second sub-prism G02 is the second reflective surface S3. The reflective function of the second reflective surface S3 is achieved by the refractive index difference between the first sub-prism G01 and the second sub-prism G02, which can reduce the coating cost. The image side of the second sub-prism G02 is the steering output surface S4. Light is incident on the steering incident surface S1, reflected from the first reflective surface S2 and the second reflective surface S3 in sequence, and finally emitted from the steering output surface S4, achieving light steering.

[0057] from Figure 3It can be seen that the steering angle of the steering prism G is θ, the angle between the steering incident surface S1 and the second reflecting surface S3 is θ1, the angle between the second reflecting surface S3 and the first reflecting surface S2 is θ2, the angle between the first reflecting surface S2 and the optical axis of the endoscope optical system is θ3, the incident angle of the light reaching the first reflecting surface S2 is θ4, and the incident angle of the light reaching the second reflecting surface S3 is θ5, which respectively satisfy: θ=30°, θ2=θ / 2, θ1+θ2+θ3+θ=90°, 6°<θ3<16°. The 30° light steering function is achieved by adjusting the shape of the sub-prism, and the degree of deflection of the light inside the steering prism G is controlled to avoid the sub-prism blocking the light, and the volume of the steering prism G can be controlled at the same time. You can choose θ3=7° or θ3=10°, which can control the turning length of the light in the steering prism G. In combination with the field of view of the optical system, it can ensure that the optical path difference between the edge field of view and the center field of view in the steering prism G is small and symmetrical, thus reducing the impact on the imaging quality. In this structure, the refractive index Nd of the first sub-prism G01 is G01 and the refractive index Nd of the second sub-prism G02 G02 You can choose to meet: Nd G01 ≤Nd G02 × sinθ5, so that the light is totally reflected on the second reflection surface S3. A better choice is to satisfy: Nd G01 ≤Nd G02 × sin(θ5-8°), this selection can make the full field of view light fully reflected at the second reflection surface S3, which can reduce the loss of light energy and reduce the coating cost.

[0058] Figure 4 The turning prism G shown is composed of a first sub-prism G01, a second sub-prism G02 and a third sub-prism G03 glued together.

[0059] The beam splitter P can be composed of three or two beam splitters.

[0060] Figure 5 The beam splitter prism P shown is composed of a first beam splitter prism P01, a second beam splitter prism P02 and a third beam splitter prism P03 glued together. The three beam splitters are made of the same material, so when the beam splitting function is not used, they can be regarded as one prism, reducing the pressure on the design of the endoscope optical system.

[0061] Films with different properties are placed on each bonding surface. Light passing through each bonding surface is split into two groups: reflected and refracted. Ultimately, information from different channels of light, such as white light, fluorescence, and polarized light, can be collected, improving the accuracy of the final imaging. White light, a commonly used wavelength, provides doctors with realistic images of the surface layer of internal tissues; fluorescence provides images of tissues below the surface, enabling precise targeting for disease treatment and reducing surgical risks. Polarized light images can block reflections from metal objects such as medical devices and scattered light from media such as saline or biological tissue, providing clearer images.

[0062] The object side surface of the first splitter prism P01 is the light splitting incident surface S5 of the splitter prism P, the bonding surface of the first splitter prism P01 and the second splitter prism P02 is defined as the first splitter surface S61, the image side surface of the first splitter prism P01 is defined as the first light splitting exit surface S71, the bonding surface of the second splitter prism P02 and the third splitter prism P03 is defined as the second light splitting exit surface S81, the image side surface of the second splitter prism P02 is defined as the second light splitting exit surface S91, and the image side surface of the third splitter prism P03 is defined as the third light splitting exit surface S101.

[0063] from Figure 5 It can be seen that the angle between the beam splitting incident surface S5 of the beam splitting prism P and the first beam splitting surface S61 is θ61, and the angle between the first beam splitting surface S61 and the second beam splitting surface S81 is θ71, which respectively satisfy: 25°<θ61<35°, 35°<θ71<45°. Controlling the angle of each prism can control the direction of light, and coordinating with the field of view angle of the optical system, so that the light of each field of view and each band is not blocked by the prism surface. The length of the first segment of light in the first prism P01 is defined as d11, the length of the first segment in the second prism P02 is defined as d21, and the length of the first segment in the third prism P03 is defined as d31. These conditions satisfy the following conditions: 0.7mm < d11 < 0.9mm, 0.9mm < d21 < 1.1mm, and 3.7mm < d11 + d21 + d31 < 3.9mm, respectively. By controlling the size of each prism, the optical path length of light in each wavelength band can be made the same, eliminating additional aberrations and meeting the requirements of different imaging focal lengths. The volume and quality of the lens can also be controlled. By satisfying the above formulas, the direction of light can be controlled by controlling the shape of each prism, ensuring that the light exit heights of each prism are close, matching the image of each prism with the detector, and ensuring the imaging quality of each field of view.

[0064] After entering the beam splitter prism P, light is reflected and refracted, producing beams of different properties. The white light beam emerges from the first beam splitter prism P01 and forms an image on the first image plane IMA1. The fluorescent light beam emerges from the second beam splitter P02 and forms an image on the second image plane IMA2. The polarized light beam emerges from the third beam splitter P03 and forms an image on the third image plane IMA3. These three signals are received by different detectors, and through subsequent fusion processing, a high-quality color image can be obtained. When the imaging focal planes of the three light beams overlap in the same endoscopic optical system, the optical path lengths of the three light beams in the respective beam splitters from which they emerge are the same. When the imaging focal planes of the three light beams do not overlap in the same endoscopic optical system, the positions of the three beam splitter exit surfaces can be slightly shifted so that the optical path lengths of the three light beams in the respective beam splitters from which they emerge are different, thereby compensating for the uneven imaging focal planes.

[0065] Figure 6 The beam splitter prism P shown is formed by gluing a first beam splitter prism P01 and a second beam splitter prism P02 together. The two beam splitters are made of the same material, so when the beam splitting function is not used, they can be regarded as one prism, reducing the pressure on the design of the endoscope optical system.

[0066] The object side surface of the first splitter prism P01 is the light splitting incident surface S5 of the splitter prism P, the bonding surface of the first splitter prism P01 and the second splitter prism P02 is defined as the first light splitting surface S62, the image side surface of the first splitter prism P01 is the first light splitting exit surface S72, and the image side surface of the second splitter prism P02 is the second light splitting exit surface S92.

[0067] from Figure 6 It can be seen that the angle between the beam splitting incident surface S5 of the beam splitting prism P and the first beam splitting surface S62 is θ62=45°. The length of the first segment of the light in the first beam splitter prism P01 is defined as d12, the length of the second segment is d22, and the length in the second beam splitter prism P02 is d32, which respectively satisfy: 2.1mm<d12<2.3mm, 1.5mm<d22<1.7mm, 1.5mm<d32<1.7mm. This can meet the imaging focal length requirements of different light rays, and by controlling the size of each beam splitter prism, the field of view angle of the optical system and the volume and quality of the lens can be controlled.

[0068] After entering the beamsplitter prism P, light is reflected and refracted, resulting in two beams: a combination of white light and fluorescent light, a combination of white light and polarized light, or a combination of fluorescent light and polarized light. The first beam of these beam combinations emerges from the first prism P01 and forms an image on the first image plane IMA1. The second beam, emerging from the second prism P02, forms an image on the second image plane IMA2. These beams are then received by different detectors and, through post-processing, fused to produce a high-quality color image.

[0069] When the imaging focal planes of two light beams overlap in the same endoscope optical system, their optical path lengths in the respective exit prisms are the same. When the imaging focal planes of two light beams do not overlap in the same endoscope optical system, the positions of the two beam splitting exit surfaces can be slightly moved to make their optical path lengths in the respective exit prisms different, thereby compensating for the misalignment of the imaging focal planes.

[0070] After the light enters the dichroic prism P, it is reflected and refracted. Only the reflected light can be used to achieve basic imaging functions.

[0071] Combining two sets of endoscope optical systems can form a four-eye or binocular endoscope optical system to obtain a three-dimensional image to match the visual habits of the human eye. Figure 14 As shown in the figure, placing two sets of reflected light receiving detectors in the middle or on both sides of the endoscope optical system can obtain a clearer image while controlling the volume. Figure 15 As shown, placing two sets of reflected light receiving detectors in the middle or on both sides of the endoscope optical system can avoid the situation where the binocular endoscope optical system is too large due to the detector being too large.

[0072] The following describes two examples in detail with reference to the accompanying drawings.

[0073] Example 1:

[0074] like Figure 1 As shown, the endoscope optical system, from the object plane to the image plane IMA, consists, in order, of a first lens L1, a turning prism G, an aperture STO, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a beam splitter P. A first protective glass GS1 and a second protective glass GS2 are also provided at each end of the endoscope optical system. In this first example, the third lens L3 has a negative optical power, a convex surface on the object side, and a concave surface on the image side. The fourth lens L4 has a positive optical power, a convex surface on the object side, and a convex surface on the image side. The fifth lens L5 has a positive optical power, a flat surface on the object side, and a convex surface on the image side.

[0075] The main optical structural parameters of the endoscope optical system of Example 1 are shown in Table 1:

[0076] Table 1

[0077]

[0078] The aspheric parameters of the endoscope optical system of Example 1 are shown in Table 2:

[0079] Table 2

[0080]

[0081] Figure 7 、 Figure 8 、 Figure 9 Table 3 shows the imaging performance of the endoscope optical system of Example 1. In the figure, the meridian of 0° coincides with the sagittal line.

[0082] like Figure 7 As shown, when the endoscope optical system of Example 1 is at a mid-object distance of 50 mm, the MTF value of the 0° central field of view is greater than 0.4, and the MTF value of the 42.8° edge field of view is greater than 0.3;

[0083] Such as Figure 8 As shown, when the endoscope optical system of Example 1 is at a close object distance of 35 mm, the MTF value of the 0° central field of view is greater than 0.3, and the MTF value of the 42.8° edge field of view is greater than 0.25;

[0084] like Figure 9 As shown, when the endoscope optical system of Example 1 has a long-range object distance of 125 mm, the MTF value of the 0° central field of view is greater than 0.2, and the MTF value of the 42.8° edge field of view is greater than 0.2;

[0085] The performance parameters of the endoscope optical system of Example 1 are shown in Table 3:

[0086] Table 3

[0087]

[0088] As shown in Table 3, the field curvature of the endoscope optical system of Example 1 is small at three object distances, the RMS radius of the imaging diffuse spot is small, and the relative illumination in the full field of view is greater than 84%.

[0089] The endoscope optical system of Example 1 has good imaging effect within a larger object distance range, and has a larger depth of field and axial resolution capability.

[0090] Example 2:

[0091] like Figure 10 As shown, the endoscope optical system, from the object plane to the image plane IMA, consists, in order, of a first lens L1, a turning prism G, an aperture STO, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a seventh lens L7, and a beam splitter P. A first protective glass GS1 and a second protective glass GS2 are also provided at each end of the endoscope optical system. In this second example, the third lens L3 has a positive optical power, with a convex object-side surface and a convex image-side surface. The fourth lens L4 has a negative optical power, with a concave object-side surface and a convex image-side surface. The fifth lens L5 has a positive optical power, with a concave object-side surface and a convex image-side surface.

[0092] The main optical structural parameters of the endoscope optical system of Example 2 are shown in Table 4:

[0093] Table 4

[0094]

[0095] The aspheric parameters of the endoscope optical system of Example 2 are shown in Table 5:

[0096] Table 5

[0097]

[0098] Figure 11 、 Figure 12 、 Figure 13 Table 6 shows the imaging performance of the endoscope optical system of Example 2. In the figure, the meridian line of 0° coincides with the sagittal line.

[0099] like Figure 11 As shown, when the endoscope optical system of Example 2 is at a mid-object distance of 50 mm, the MTF value of the 0° central field of view is greater than 0.4, and the MTF value of the 42.8° edge field of view is greater than 0.3;

[0100] like Figure 12 As shown, when the endoscope optical system of Example 2 is at a close object distance of 35 mm, the MTF value of the 0° central field of view is greater than 0.3, and the MTF value of the 42.8° edge field of view is greater than 0.29;

[0101] like Figure 13 As shown, the endoscope optical system of Example 2 has an MTF value greater than 0.2 at the 0° center field of view and greater than 0.25 at the 42.8° edge field of view at a long-range object distance of 125 mm. Compared with Example 1, the imaging resolution is slightly improved.

[0102] The main performance parameters of the endoscope optical system of Example 2 are shown in Table 6:

[0103] Table 6

[0104]

[0105] As shown in Table 6, the field curvature of the endoscope optical system of Example 2 is small at three object distances, the RMS radius of the imaging diffuse spot is small, and the relative illumination in the entire field of view is greater than 91%, which is an improvement compared with the endoscope optical system of Example 1.

[0106] The endoscope optical system of Example 2 has a good imaging effect within a larger object distance range, and has a larger depth of field and axial resolution capability.

[0107] The above is only an example of the present invention and does not limit the scope of protection of the present invention. Equivalent changes made according to the scope of the patent application of the present invention still fall within the scope of the present invention.

Claims

1. An endoscope optical system, characterized in that From the object plane to the image plane, it consists of a first lens, a turning prism, an aperture, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a dichroic prism. The optical power of the first lens is negative, the object side is convex, and the image side is concave; the optical power of the second lens is positive, the object side is flat, and the image side is convex; the object side of the third lens is convex, the optical power of the fourth lens is opposite to that of the third lens, and the image side is convex; the optical power of the fifth lens is positive, and the image side is convex; the optical power of the sixth lens is negative, the object side is concave, and the image side is concave; the optical power of the seventh lens is positive, and the object side is convex, and the image side is convex; the object-side numerical aperture NA of the endoscope optical system satisfies: 0.001<NA<0.

006.

2. An endoscope optical system according to claim 1, characterized in that Both surfaces of the first lens are aspherical.

3. An endoscope optical system according to claim 1, characterized in that The third lens and the fourth lens form a doublet lens, and the fifth lens, the sixth lens and the seventh lens form a triplet lens.

4. An endoscope optical system according to claim 3, characterized in that The focal length f of the endoscope optical system and the focal length f of the first lens are L1 The focal length of the second lens is f L2 The focal length f of the doublet lens 34 The focal length f of the triplet lens 567 Satisfy respectively: -0.8<f L1 / f<-0.7,1.5<f L2 / f<1.7,3.2<f 34 / f<3.5,f 567 / f=-863461.26 or f 567 / f=-9455.

35.

5. An endoscope optical system according to claim 1, characterized in that The refractive index of the material of the first lens is defined as Nd L1 The refractive index of the second lens is Nd L2 The refractive index of the third lens is Nd L3 The refractive index of the fourth lens is Nd L4 The refractive index of the material of the fifth lens is Nd L5 The refractive index of the sixth lens is Nd L6 The refractive index of the seventh lens is Nd L7 , respectively satisfying: 1.9<Nd L1 <2.1,1.6<Nd L2 <1.8,0.15<|Nd L3 -Nd L4 |<0.25,0.15<|Nd L5 -Nd L6 |<0.25,0.15<|Nd L6 -Nd L7 |<0.

25.

6. An endoscope optical system according to claim 1, characterized in that The steering prism is provided with a steering incident surface, a first reflection surface, a second reflection surface and a steering output surface. The steering output surface is located between the first reflection surface and the second reflection surface and is perpendicular to the optical axis of the endoscope optical system. The light is vertically incident on the steering incident surface and is incident on the first reflection surface at a first incident angle. It is reflected by the first reflection surface and is incident on the second reflection surface at a second incident angle. It is then reflected by the second reflection surface to the steering output surface and then vertically exits. The steering angle of the steering prism is defined as θ, the angle between the steering incident surface and the second reflection surface is θ1, the angle between the second reflection surface and the first reflection surface is θ2, and the angle between the first reflection surface and the optical axis of the endoscope optical system is θ3, which respectively satisfy the following relationships: θ=30°, θ2=θ / 2, θ1+θ2+θ3+θ=90°, 6°<θ3<16°.

7. An endoscope optical system according to claim 6, characterized in that The turning prism is a single prism, and the angle θ3 between the first reflecting surface and the optical axis of the endoscope optical system is 15°.

8. An endoscope optical system according to claim 6, characterized in that The turning prism is composed of a first sub-prism and a second sub-prism glued together, the turning incident surface is the object side of the first sub-prism, the first reflection surface is in contact with the air, the second reflection surface is the glued surface of the first sub-prism and the second sub-prism, the turning exit surface is the image side of the second sub-prism, and the angle θ3=7° or θ3=10° between the first reflection surface and the optical axis of the endoscope optical system.

9. An endoscope optical system according to claim 8, characterized in that The first reflective surface is coated with a reflective film, and the refractive index of the first sub-prism is defined as Nd G01 The refractive index of the second sub-prism is Nd G02 , the second incident angle is θ5, satisfying: Nd G01 ≤Nd G02 ×sinθ5.

10. An endoscope optical system according to claim 8, characterized in that The refractive index of the first sub-prism is defined as Nd G01 The refractive index of the second sub-prism is Nd G02 , the second incident angle is θ5, satisfying: Nd G01 ≤Nd G02 ×sin(θ5-8°).

11. An endoscope optical system according to claim 1, characterized in that The dichroic prism is formed by gluing together multiple dichroic prisms made of the same material. The gluing surfaces of the various dichroic prisms serve as dichroic surfaces. The light emitted from the seventh lens enters the dichroic incident surface of the dichroic prism and is then split into light of different properties on different dichroic surfaces, and then is emitted from the dichroic exit surfaces of different dichroic prisms in the dichroic prism.

12. An endoscope optical system according to claim 11, characterized in that The beam splitter prism is formed by gluing together three first, second and third prisms made of the same material. The object side of the first prism is the beam splitting incident surface of the beam splitter prism. The gluing surface of the first prism and the second prism is defined as the first beam splitting surface. The image side of the first prism is defined as the first beam splitting exit surface. The gluing surface of the second prism and the third prism is defined as the second beam splitting surface. The image side of the second prism is defined as the second beam splitting exit surface. The image side of the third prism is defined as the third beam splitting exit surface. The beam splitting incident surface and the beam splitting surface of the beam splitter prism are defined as the first beam splitting exit surface. The included angle of the first beam splitting surface is θ61, and the included angle between the first beam splitting surface and the second beam splitting surface is θ71, which respectively satisfy: 25°<θ61<35°, 35°<θ71<45°; the length of the first segment of the light in the first beam splitting prism is defined as d11, the length of the first segment in the second beam splitting prism is defined as d21, and the length of the first segment in the third beam splitting prism is defined as d31, which respectively satisfy: 0.7mm<d11<0.9mm, 0.9mm<d21<1.1mm, 3.7mm<d11+d21+d31<3.9mm.

13. An endoscope optical system according to claim 11, characterized in that The dichroic prism is formed by gluing a first dichroic prism and a second dichroic prism made of the same material. The object side of the first dichroic prism is the dichroic incident surface of the dichroic prism. The gluing surface of the first dichroic prism and the second dichroic prism is defined as the first dichroic surface. The image side of the first dichroic prism is the first dichroic exit surface, and the image side of the second dichroic prism is the second dichroic exit surface. The angle between the dichroic incident surface of the dichroic prism and the first dichroic surface is θ62=45°. The length of the first segment of the light in the first dichroic prism is defined as d12, the length of the second segment is defined as d22, and the length of the light in the second dichroic prism is defined as d32, which respectively satisfy the following: 2.1mm<d12<2.3mm, 1.5mm<d22<1.7mm, and 1.5mm<d32<1.7mm.

Images