Three-band endoscope optical system

Abstract

The invention relates to the technical field of optical imaging, in particular to a three-band endoscope optical system which comprises a camera adapter located on one side of an optical observation mirror, and the optical observation mirror sequentially comprises an objective lens set, a relay image rotating rod lens set and an ocular lens set and is used for broadband achromatism. Three-waveband confocal plane imaging of visible light, a first near-infrared region and a second near-infrared region is realized; the camera adapter is used for carrying out light splitting imaging on the parallel light transmitted by the optical observation mirror; wherein the objective lens group comprises a front-end negative group and a rear-end positive group, and the front-end negative group adopts a lens with negative focal power, high refractive index and low dispersion, so that large-view-field imaging and inter-band chromatic aberration elimination are realized; the rear-end positive group can correct spherical aberration and position chromatic aberration by adopting a plurality of bonding lenses with positive focal power, and can compensate mutually with the front-end negative group to jointly correct coma, astigmatism and field curvature; the near-infrared two-region wave band is applied to the hard tube endoscope, so that the detection capability of the hard tube endoscope on deep tiny focuses is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and particularly to a three-band endoscope optical system. Background Art

[0002] A fluorescence endoscope is a medical device applied to minimally invasive surgery. Due to its unique advantages in minimally invasive surgery, it has been more and more widely used. The fluorescence endoscope injects a fluorescence probe and uses incident light to excite the fluorescence probe in the lesion tissue, and displays the position of the lesion tissue in real time, thereby assisting the doctor in performing precise resection. Currently, common fluorescence endoscopes include rigid endoscopes and flexible endoscopes.

[0003] Traditional fluorescence endoscopes mainly use visible light and near-infrared region I (NIR-I, 800nm - 900nm) for imaging. The penetration ability of NIR-I in tissues is limited, making it difficult to detect deep and tiny lesions, which limits its detection sensitivity to lesions. With the development of fluorescence imaging technology, near-infrared region II (NIR-II, 1000nm - 1700nm) band imaging shows broad application prospects in the field of biomedicine. Compared with the visible light and NIR-I bands, the NIR-II band has a longer wavelength, smaller light scattering and absorption in biological tissues, can achieve deeper tissue penetration, and has higher detection sensitivity.

[0004] For example, Chinese Utility Model Patent CN221105783U discloses a wide-spectrum fluorescence endoscope optical system, including a beam splitting module, a visible light imaging module, a near-infrared region II imaging module, a laser transmission optical fiber, and a wide-spectrum endoscope barrel connected to the laser transmission optical fiber. Among them, the wide-spectrum endoscope barrel is an optical system with an antireflection band covering a wide spectrum range of 400nm to 1700nm; the beam splitting module is located on one side of the wide-spectrum endoscope barrel; the visible light imaging module is located on one side of the beam splitting module, and the near-infrared region II imaging module is located on one side of the beam splitting module. This patent only performs flat-field achromatic imaging on the imaging beam through the visible light imaging module and the near-infrared region II imaging module, thereby realizing fluorescence detection in the near-infrared region II.

[0005] However, traditional rigid endoscopes have high requirements for the above-mentioned endoscope barrel, such as large-field imaging, correction of spherical aberration, position chromatic aberration, coma, astigmatism, and field curvature. The optical imaging structure of existing traditional rigid endoscopes, such as a rigid endoscope with an aspherical lens group disclosed in Chinese Invention Patent CN102004309B, sequentially includes an objective lens system and an eyepiece system along the optical axis direction. A symmetric rod lens group is provided between the objective lens system and the eyepiece system. The rod lens group includes two identical rod-shaped lenses and negative lenses installed at both ends of each rod-shaped lens. However, this patent uses a symmetric rod lens group, which will increase the accumulation of axial chromatic aberration.

[0006] Therefore, it is urgent to improve the optical imaging part of the rigid endoscope to meet the imaging requirements of visible light, NIR-I, and NIR-II in the rigid endoscope. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defects and deficiencies in the prior art. Therefore, the present invention provides a three-band endoscope optical system, which can realize confocal plane imaging in three bands of visible light, NIR-I, and NIR-II, achieve large field of view imaging, correct spherical aberration, longitudinal chromatic aberration, coma, astigmatism, and field curvature, and finally image visible light, NIR-I, and NIR-II on the corresponding sensors.

[0008] To achieve the above purpose, the present invention provides a three-band endoscope optical system, including a camera adapter located on one side of the optical observation mirror. The optical observation mirror sequentially includes an objective lens group, a relay image rotation rod lens group, and an eyepiece group along the optical axis direction. The imaging band of the optical observation mirror is 486nm - 1700nm, and confocal plane imaging is achieved in three bands of visible light, NIR-I, and NIR-II. The camera adapter performs three-band spectral imaging on the parallel light transmitted by the optical observation mirror.

[0009] The objective lens group includes a front negative group and a rear positive group. The front negative group is sequentially composed of a first protective glass, a first lens, and a second lens, all of which have negative optical power, and the refractive index of the first lens is greater than 1.8. The rear positive group is sequentially composed of a first cemented lens, a second cemented lens, a third cemented lens, and a fourth cemented lens, all of which have positive optical power.

[0010] Further, the front end of the objective lens is the first protective glass; the first lens is a meniscus negative lens with a concave rear surface; the second lens is a plano-concave lens with a concave front surface; the first cemented lens is sequentially composed of a beam deflector and a plano-convex lens with a flat front surface; the second cemented lens is sequentially composed of a biconvex lens and a plano-concave lens with a concave front surface; the third cemented lens is sequentially composed of a meniscus negative lens with a concave rear surface, a biconvex lens, and a meniscus negative lens with a concave front surface; the fourth cemented lens is sequentially composed of a meniscus negative lens with a concave rear surface and a biconvex lens. The beam deflector is a flat glass or a steering prism and is used to realize different viewing angles of the endoscope.

[0011] Further, the relay image rotation rod lens group sequentially includes three rod lens groups with exactly the same structure along the optical axis direction. Each rod lens group sequentially includes a fifth cemented lens and a sixth cemented lens along the optical axis direction.

[0012] The fifth cemented lens is composed of a biconvex rod lens, a meniscus positive lens with a concave front end, a biconcave lens, and a biconvex lens that are sequentially and adhesively combined along the optical axis direction; the sixth cemented lens is composed of a biconvex lens, a biconcave lens, a meniscus positive lens with a convex front end, and a biconvex rod lens that are sequentially and adhesively combined along the optical axis direction; the fifth cemented lens and the sixth cemented lens are arranged in an asymmetric structure.

[0013] Further, the eyepiece group sequentially includes a seventh cemented lens, an eighth cemented lens, and a second protective glass along the optical axis direction;

[0014] The seventh cemented lens is composed of a biconvex lens and a biconcave lens that are sequentially and adhesively combined; the eighth cemented lens is composed of a biconvex lens, a biconcave lens, and a biconvex lens that are sequentially and adhesively combined.

[0015] Further, the camera adapter includes a visible light / NIR-I branch and an NIR-II branch; the visible light / NIR-I branch and the NIR-II branch are respectively located on two mutually perpendicular sides of the beam splitter;

[0016] The visible light / NIR-I branch sequentially includes a ninth cemented lens, a tenth cemented lens, a third lens, and a beam splitting prism located on one side of the beam splitter; the beam splitting prism is used for secondary beam splitting and imaging on the visible light image plane S1 and the NIR-I image plane S2 respectively;

[0017] The NIR-II branch sequentially includes an eleventh cemented lens, a twelfth cemented lens, and a fourth lens located on one side of the beam splitter; the NIR-II branch images on the NIR-II image plane S3.

[0018] Further, both the ninth cemented lens and the eleventh cemented lens are composed of a plano-concave lens with a concave front end and a plano-convex lens with a convex rear end that are sequentially and adhesively combined; both the tenth cemented lens and the twelfth cemented lens are composed of a plano-convex lens with a convex rear end, a biconcave lens, and a biconvex lens that are sequentially and adhesively combined; the third lens and the fourth lens are both meniscus positive lenses with a convex front end.

[0019] Further, the optical observation mirror and the camera adapter are detachably connected through an eyepiece and a bayonet, and the exit pupil of the optical observation mirror corresponds to the entrance pupil of the camera adapter; the diameter of the entrance pupil of the camera adapter is not less than the diameter of the exit pupil of the optical observation mirror, and the entrance pupil field angle is not less than the exit pupil field angle of the optical observation mirror.

[0020] Further, the objective lens group is an image-space telecentric structure, the relay image-rotating rod lens group is a double telecentric structure, the eyepiece group is an object-space telecentric structure, the image plane of the objective lens group is connected to the object plane of the relay image-rotating rod lens group, and the object plane of the relay image-rotating rod lens group is connected to the object plane of the eyepiece group.

[0021] Furthermore, both the first protective glass and the second protective glass are made of sapphire glass.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: By using lenses with negative optical power and high refractive index in the front negative group, the inclination angle of the light beam relative to the optical axis can be effectively reduced, thereby achieving large-field imaging; in the rear positive group, through the first cemented lens, the second cemented lens, the third cemented lens, and the fourth cemented lens with positive optical power, spherical aberration and axial chromatic aberration can be corrected, and they can compensate with the front negative group to jointly correct coma, astigmatism, and field curvature. At the same time, the NIR-II band is applied to the rigid endoscope to achieve composite imaging in the visible light, NIR-I, and NIR-II bands. By taking advantage of the small scattering and large detection depth of the NIR-II band in tissues, the detection ability of the rigid endoscope for deep-seated micro-lesions is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the present invention;

[0024] Figure 2 is Figure 1 a schematic structural diagram of the optical observation mirror in

[0025] Figure 3 is Figure 2 a schematic structural diagram of the objective lens group in

[0026] Figure 4 is Figure 2 a schematic structural diagram of the rod lens group in

[0027] Figure 5 is Figure 2 a schematic structural diagram of the eyepiece group in

[0028] Figure 6 is Figure 1 a schematic structural diagram of the camera adapter in

[0029] Figure 7 It is the spot diagram of the present invention in the visible light band;

[0030] Figure 8 It is the spot diagram of the present invention in the NIR-I band;

[0031] Figure 9 It is the spot diagram of the present invention in the NIR-II band;

[0032] Figure 10 It is the MTF curve diagram of the present invention in the visible light band;

[0033] Figure 11 It is the MTF curve diagram of the present invention in the NIR-I band;

[0034] Figure 12 This is the MTF curve graph of the present invention in the NIR-II band;

[0035] Figure 13 It shows the light fluxes of NIR-I and NIR-II received on the detector surface when tumors with a radius of 7 mm and 0.5 mm are located at different tissue depths. (Among them, (a) is a tumor with a radius of 0.5 mm; (b) is a tumor with a radius of 7 mm).

[0036] Wherein: 10, optical observation mirror; 20, camera adapter; 11, objective lens group; 12, relay image-rotating rod lens group; 13, eyepiece group; 21, visible light / NIR-I branch; 22, NIR-II branch; 110, first protective glass; 111, first lens; 112, second lens; 113, first cemented lens; 114, second cemented lens; 115, third cemented lens; 116, fourth cemented lens; 120, fifth cemented lens; 121, sixth cemented lens; 130, seventh cemented lens; 131, eighth cemented lens; 132, second protective glass; 210, beam splitter; 211, ninth cemented lens; 212, tenth cemented lens; 213, third lens; 214, beam splitting prism; 221, eleventh cemented lens; 222, twelfth cemented lens; 223, fourth lens. Detailed implementation manners

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0039] Embodiment

[0040] Please refer to Figures 1 to 6, the present invention provides a three - band endoscope optical system, which includes two parts: an optical viewing scope 10 and a camera adapter 20. Among them, the optical viewing scope 10 is used for imaging an object and emits parallel light at the rear end for direct observation by the human eye; the camera adapter is used to divide the parallel light transmitted from the optical viewing scope into three bands: visible light, NIR - Ⅰ, and NIR - Ⅱ, and image them on their respective image sensors.

[0041] As Figure 2 shown, the optical viewing scope 10 is sequentially divided into an objective lens group 11, a relay image - rotating rod lens group 12, and an eyepiece group 13 along the optical path propagation (i.e., along the optical axis direction). The optical viewing scope 10 performs broadband achromatism in the 486nm - 1700nm band, realizing confocal imaging in three bands: visible light (486nm - 656nm), NIR - Ⅰ (800nm - 900nm), and NIR - Ⅱ (1000nm - 1700nm).

[0042] Specifically, as Figure 3 shown, the objective lens group 11 sequentially includes a first protective glass 110, a first lens 111, a second lens 112, a first cemented lens 113, a second cemented lens 114, a third cemented lens 115, and a fourth cemented lens 116 from the object side to the image side (i.e., along the optical axis direction).

[0043] Among them, in the direction of the optical path propagation: the first protective glass 110 is at the forefront; the first lens 111 is a meniscus negative lens with a concave rear surface; the second lens 112 is a plano - concave lens with a concave front surface; the first cemented lens 113 is a doublet cemented lens composed of a flat glass and a plano - convex lens with a flat front surface sequentially matched and cemented; the second cemented lens 114 is a doublet cemented lens composed of a biconvex lens and a plano - concave lens with a concave front surface sequentially matched and cemented; the third cemented lens 115 is a triplet cemented lens composed of a meniscus negative lens with a concave rear surface, a biconvex lens, and a meniscus negative lens with a concave front surface sequentially matched and cemented; the fourth cemented lens 116 is a doublet cemented lens composed of a meniscus negative lens with a concave rear surface and a biconvex lens sequentially matched and cemented.

[0044] The flat glass in the above - mentioned first cemented lens 113 can be replaced by a steering prism to achieve different viewing angles of the endoscope. Here, the flat glass or the steering prism is used as a beam deflector.

[0045] The objective lens group 11 here is divided into a front negative group and a rear positive group. The front negative group is composed of a first protective glass 110, a first lens 111, and a second lens 112; among them, both the first lens 111 and the second lens 112 have negative optical powers, and the refractive index of the first lens is greater than 1.8. By using lenses with negative optical powers and high refractive indices in this front negative group, the inclination angle of the light beam relative to the optical axis can be effectively reduced, thereby achieving large-field imaging; at the same time, materials with high refractive indices and low dispersions can be selected for the front negative group to meet the requirements of eliminating chromatic aberration between bands.

[0046] The rear positive group consists of a first cemented lens 113, a second cemented lens 114, a third cemented lens 115, and a fourth cemented lens 116, all of which have positive optical powers. This rear positive group is responsible for converging the light beam. Due to the diverging effect of the front negative group on the light beam, the rear positive group has a relatively large clear aperture, which will introduce relatively large spherical aberration and longitudinal chromatic aberration. Therefore, by using doublets and triplets for the lenses in the rear positive group, spherical aberration and longitudinal chromatic aberration are corrected, and the rear positive group and the front negative group can compensate each other to jointly correct coma, astigmatism, and field curvature.

[0047] As an embodiment of the present invention, as Figure 2 shown, the relay image-rotating rod lens group 12 includes three rod lens groups with exactly the same structure. As Figure 4 shown, each rod lens group sequentially includes a fifth cemented lens 120 and a sixth cemented lens 121 along the optical axis direction; the fifth cemented lens 120 and the sixth cemented lens 121 are arranged in an asymmetric structure.

[0048] The rod lens groups here are used to extend the optical path to meet the requirements for the working length in the use of endoscopes.

[0049] The above-mentioned fifth cemented lens 120 is preferably a four-cemented lens composed of a double-convex rod lens, a meniscus positive lens with a concave front surface, a double-concave lens, and a double-convex lens sequentially matched and cemented along the optical axis direction; the sixth cemented lens 121 is preferably a four-cemented lens composed of a double-convex lens, a double-concave lens, a meniscus positive lens with a convex front surface, and a double-convex rod lens sequentially matched and cemented along the optical axis direction. Compared with the existing rod lens groups with symmetric structures, by adopting an asymmetric structure design for each rod lens group of the relay image-rotating rod lens group 12, that is, the corresponding fifth cemented lens 120 and sixth cemented lens 121 are no longer strictly symmetric in terms of radius of curvature, lens material, and lens thickness, the accumulation of axial chromatic aberrations such as astigmatism and field curvature in the relay image-rotating rod lens group 12 is reduced. At the same time, the relay image-rotating rod lens group 12 and the objective lens group 11 compensate each other to correct the overall aberration.

[0050] As an embodiment of the present invention, as Figure 5As shown, the eyepiece group 13 includes a seventh cemented lens 130, an eighth cemented lens 131, and a second protective glass 132 in sequence from the object side to the image side. Among them, the seventh cemented lens consists of a double convex lens and a double concave lens to form a doublet; the eighth cemented lens consists of a double convex lens, a double concave lens, and a double convex lens in sequence to form a triplet; the rearmost is the second protective glass.

[0051] During the use of the present invention, multiple image plane transmissions are required, and it is necessary to ensure good connection between the image plane of the front group structure and the object plane of the rear group structure in the optical system. Therefore, the above-mentioned objective lens group 11 preferably adopts an image-side telecentric structure, the relay image transfer rod lens group 12 preferably adopts a double telecentric structure, and the eyepiece group 13 preferably adopts an object-side telecentric structure, so as to ensure the connection of the image plane between the objective lens group 11 and the relay image transfer rod lens group 12, and the connection of the object plane between the relay image transfer rod lens group 12 and the eyepiece group 13.

[0052] As an embodiment of the present invention, as Figure 6 shown, the camera adapter 20 includes a visible light / NIR-I branch 21 and an NIR-II branch 22; among them, the visible light / NIR-I branch 21 and the NIR-II branch 22 are both located on two mutually perpendicular sides of the beam splitter 210.

[0053] The above-mentioned visible light / NIR-I branch 21 sequentially includes a ninth cemented lens 211, a tenth cemented lens 212, a third lens 213, and a beam splitting prism 214 located on one side of the beam splitter 210; the beam splitting prism 214 is used for secondary beam splitting and imaging on the visible light image plane S1 and the NIR-I image plane S2.

[0054] The above-mentioned NIR-II branch 22 sequentially includes an eleventh cemented lens 221, a twelfth cemented lens 222, and a fourth lens 223 located on one side of the beam splitter 210; the NIR-II branch 22 images on the NIR-II image plane S3.

[0055] Specifically, both the ninth cemented lens 211 and the eleventh cemented lens 221 are doublets composed of a plano-concave lens with a concave front end and a plano-convex lens with a convex rear end sequentially matched and cemented; both the tenth cemented lens 212 and the twelfth cemented lens 222 are triplets composed of a plano-convex lens with a convex rear end, a double concave lens, and a double convex lens sequentially matched and cemented; both the third lens 213 and the fourth lens 223 are meniscus positive lenses with a convex front end.

[0056] Compared with the NIR-II branch 22, the above-mentioned visible light / NIR-Ⅰ branch 21 has the same optical structure except that the NIR-Ⅱ branch 22 has no beam splitter prism 214, that is, the position, air spacing and structure of the ninth cemented lens 211, the tenth cemented lens 212 and the fourth lens 213 are the same as those of the eleventh cemented lens 221, the twelfth lens 222 and the sixth lens 223. The air spacing between each lens in the two branches is the same, so that the image size of visible light, NIR-Ⅰ and NIR-Ⅱ on the detector can be guaranteed to be consistent, which is convenient for subsequent image processing.

[0057] The parallel light from the optical observation scope 10 is split by the beam splitter 210, and can be divided into the visible light / NIR-Ⅰ branch 21 of the 486nm-900nm band and the NIR-Ⅱ branch 22 of the 1000nm-1700nm band. The visible light / NIR-Ⅰ branch 21 is split by the beam splitter prism 214, and can be divided into the visible light of the 486nm-656nm band and the NIR-Ⅰ of the 800nm-900nm band, so as to ensure that the three bands are imaged on the corresponding image sensors respectively, that is, the visible light image plane S1, the NIR-Ⅰ image plane S2 and the NIR-Ⅱ image plane S3 are imaged on the corresponding image sensors. Among them, the visible light / NIR-Ⅰ branch 21 can be adapted to the current medical fluorescence endoscope camera system, and the NIR-Ⅱ branch 22 is connected to the InGaAs camera.

[0058] In addition, the camera adapter and the optical observation mirror are detachably connected through the existing eye mask and bayonet, and the optical connection method is pupil connection, that is, the exit pupil of the optical observation mirror 10 corresponds to the entrance pupil of the camera adapter 20, and at the same time, it is ensured that the entrance pupil diameter of the camera adapter 20 is not less than the exit pupil diameter of the optical observation mirror, and the entrance pupil field of view angle is not less than the exit pupil field of view angle of the optical observation mirror 10.

[0059] In addition, the first protective glass 110 at the front end of the objective lens group 11 and the second protective glass 132 at the rear end of the eyepiece group 13 are both made of sapphire glass as protective glass. The high hardness of sapphire can effectively protect the optical elements of the endoscope.

[0060] like Figure 7 , Figure 8 and Figure 9 As shown, the spot diagrams of the present invention in the three bands of visible light, NIR-Ⅰ, and NIR-Ⅱ are shown. In the full field of view of the three bands of visible light, NIR-Ⅰ, and NIR-Ⅱ, the root mean square radius and geometric radius of the diffuse spot are both smaller than the radius of the Airy disk, which indicates that the imaging quality is good.

[0061] like Figure 10 , Figure 11 and Figure 12As shown, they are respectively the MTF curve graphs of the present invention in three bands of visible light, NIR-I, and NIR-II. In the visible light band, when the spatial frequency is 145 lp / mm, the MTF values within the full field of view are all greater than 0.1; in the NIR-I band, when the spatial frequency is 77 lp / mm, the MTF values are all greater than 0.3 except for the maximum field of view; in the NIR-II band, when the spatial frequency is 50 lp / mm, the MTF values within the full field of view are all above 0.2. In the full field of view of the present invention, the MTF values in the three bands of visible light, NIR-I, and NIR-II are all close to the diffraction limit.

[0062] In summary, the present invention applies NIR-II to the design of a rigid endoscope, and realizes the confocal plane design for three bands of visible light, NIR-I, and NIR-II through the optical observation mirror 10; by dividing the camera adapter 20 into a visible light / NIR-I branch 21 and an NIR-II branch 22, imaging for three bands of visible light, NIR-I, and NIR-II is realized respectively. Utilizing the advantages of NIR-II imaging, the endoscope can detect deeper lesion tissues and has better lesion detection performance.

[0063] Specifically, according to the simulation setting parameters shown in Table 1 and the detector input parameters shown in Table 2, simulate the fluorescence excitation characteristics of tumors stained with ICG in the tissue, and use the three-band fluorescence endoscope containing the present invention to receive the excited fluorescence, and analyze the detection depth difference of the present invention for tumor lesions in NIR-I and NIR-II. As Figure 13 shown, the light fluxes of NIR-I and NIR-II received on the detector surface when tumors with a radius of 7 mm and 0.5 mm are located at different tissue depths are obtained, that is, the fluorescence light fluxes received by the NIR-II branch are all higher than those received by the NIR-I branch.

[0064] Table 1 Simulation setting parameters

[0065] Parameter name Parameter value Refractive index of tissue 1.368 <![CDATA[Reduced scattering coefficient of tissue / cm -1 > 0.32 <![CDATA[Tissue absorption coefficient / cm -1 > 41.4 Isotropic coefficient of tissue 0.95 Fluorescent quantum conversion efficiency 0.8 Incident light wavelength / nm 808 Incident light power / W 2 Incident light divergence angle / ° 45 Distance between incident light and tissue surface / mm 20

[0066] Table 2 Detector input parameters

[0067]

[0068] According to the simulation results on the detector surface, the signal-to-noise ratios of NIR-I and NIR-II on their respective detectors are obtained. Among them, the InGaAs detector used for NIR-II is calculated under the conditions of refrigeration at -20 °C and -80 °C, and the signal-to-noise ratios of two sizes of tumors at different depths are obtained. Specifically, as shown in Table 3 and Table 4, d represents the tumor depth. The signal-to-noise ratios of NIR-II at refrigeration of -20 °C and -80 °C are greater than the signal-to-noise ratios of NIR-I at the same depth, indicating that the application of the NIR-II band in a rigid endoscope can improve the detection performance for tumors.

[0069] Table 3 Signal-to-noise ratio when tumors with a radius of 0.5 mm are located at different depths in the tissue

[0070]

[0071] Table 4 Signal-to-noise ratio when tumors with a radius of 7 mm are located at different depths in the tissue

[0072]

[0073] The present invention can be summarized in other specific forms without departing from the spirit or main features of the present invention. Therefore, from any point of view, the above embodiments of the present invention can only be considered as an illustration of the present invention and cannot limit the present invention. The claims point out the scope of the present invention, while the above description does not point out the scope of the present invention. Therefore, any change within the meaning and scope equivalent to the claims of the present invention should be considered as being included within the scope of the claims of the present invention.

Claims

1. A three-band endoscope optical system, comprising a camera adapter (20) located on one side of an optical observation mirror (10), wherein the optical observation mirror (10) comprises an objective lens group (11), a relay image rod lens group (12) and an eyepiece lens group (13) in sequence along the optical axis direction, characterized in that: The imaging band of the optical observation mirror (10) is 486nm-1700nm, and confocal imaging is performed in three bands: visible light, NIR-I, and NIR-II; the camera adapter (20) performs three-band spectral imaging on the parallel light transmitted from the optical observation mirror (10); The objective lens group (11) comprises a front negative group and a rear positive group; the front negative group is sequentially composed of a first protective glass (110) and a first lens (111) and a second lens (112) both of which have negative optical power along the optical axis direction, and the refractive index of the first lens (111) is greater than 1.8; the rear positive group is sequentially composed of a first cemented lens (113), a second cemented lens (114), a third cemented lens (115) and a fourth cemented lens (116) both of which have positive optical power along the optical axis direction.

2. The three-band endoscope optical system according to claim 1, characterized in that: The first lens (111) is a meniscus-shaped negative lens with a concave rear end surface; the second lens (112) is a plano-concave lens with a concave front end surface; the first cemented lens (113) is composed of a beam deflector and a plano-convex lens on a front end plane matched and glued in sequence; the second cemented lens (114) is composed of a biconvex lens and a plano-concave lens on a concave front end surface matched and glued in sequence; the third cemented lens (115) is composed of a meniscus-shaped negative lens with a concave rear end surface, a biconvex lens and a meniscus-shaped negative lens on a concave front end surface matched and glued in sequence; the fourth cemented lens (116) is composed of a meniscus-shaped negative lens with a concave rear end surface and a biconvex lens matched and glued in sequence; the beam deflector is a flat glass or a steering prism, and is used to achieve different viewing angles of the endoscope.

3. The three-band endoscope optical system according to claim 1 or 2, characterized in that: The relay image-transmitting rod lens group (12) comprises three rod lens groups with completely identical structures in sequence along the optical axis direction; each rod lens group comprises a fifth cemented lens (120) and a sixth cemented lens (121) in sequence along the optical axis direction; The fifth cemented lens (120) is composed of a double convex rod mirror, a meniscus positive lens with a concave front end, a double concave lens and a double convex lens matched and glued in sequence along the optical axis direction; the sixth cemented lens (121) is composed of a double convex lens, a double concave lens, a meniscus positive lens with a convex front end and a double convex rod mirror matched and glued in sequence along the optical axis direction; the fifth cemented lens (120) and the sixth cemented lens (121) are arranged in an asymmetric structure.

4. The three-band endoscope optical system according to claim 3, characterized in that: The eyepiece group (13) comprises, in sequence along the optical axis direction, a seventh cemented lens (130), an eighth cemented lens (131) and a second protective glass (132); The seventh cemented lens (130) is composed of a biconvex lens and a biconcave lens matched and glued together in sequence; the eighth cemented lens (131) is composed of a biconvex lens, a biconcave lens, and a biconvex lens matched and glued together in sequence.

5. The three-band endoscope optical system according to claim 4, characterized in that: The camera adapter (20) comprises a visible light / NIR-I branch (21) and a NIR-II branch (22); the visible light / NIR-I branch (21) and the NIR-II branch (22) are respectively located on two sides of the beam splitter (210) that are perpendicular to each other; The visible light / NIR-I branch (21) comprises in sequence a ninth cemented lens (211), a tenth cemented lens (212), a third lens (213) and a beam splitter prism (214) located on one side of the beam splitter (210); the beam splitter prism (214) is used for secondary light splitting and forming images on the visible light image plane S1 and the NIR-I image plane S2 respectively; The NIR-II branch (22) comprises, in sequence, an eleventh cemented lens (221), a twelfth cemented lens (222), and a fourth lens (223) located on one side of the beam splitter (210); the NIR-II branch (22) forms an image on the NIR-II image plane S3.

6. The three-band endoscope optical system according to claim 5, characterized in that: The ninth cemented lens (211) and the eleventh cemented lens (221) are both composed of a plano-concave lens with a concave front end surface and a plano-convex lens with a convex rear end surface, which are matched and glued together in sequence; the tenth cemented lens (212) and the twelfth cemented lens (222) are both composed of a plano-convex lens with a convex rear end surface, a biconcave lens, and a biconvex lens, which are matched and glued together in sequence; the third lens (213) and the fourth lens (223) are both meniscus positive lenses with a convex front end surface.

7. The three-band endoscope optical system according to claim 6, characterized in that: The optical observation mirror (10) and the camera adapter (20) are detachably connected via an eye mask and a bayonet; an exit pupil of the optical observation mirror (10) corresponds to an entrance pupil of the camera adapter (20); the entrance pupil diameter of the camera adapter (20) is not less than the exit pupil diameter of the optical observation mirror (10), and the entrance pupil field of view angle is not less than the exit pupil field of view angle of the optical observation mirror (10).

8. The three-band endoscope optical system according to claim 7, characterized in that: The objective lens group (11) is an image-side telecentric structure, the relay image rod lens group (12) is a double telecentric structure, and the eyepiece group (13) is an object-side telecentric structure. The image plane of the objective lens group (11) is connected to the object plane of the relay image rod lens group (12), and the image plane of the relay image rod lens group (12) is connected to the object plane of the eyepiece group (13).

9. The three-band endoscope optical system according to claim 4, characterized in that: The first protective glass (110) and the second protective glass (132) are both made of sapphire glass.

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