Objective lens optical system for paranasal sinus endoscope

Abstract

The invention discloses an objective optical system for a paranasal sinus endoscope, which comprises a first lens group with negative focal power, a second lens group with positive focal power, a diaphragm, a third lens group with negative focal power and a fourth lens group with positive focal power in sequence from an object side, and meets the following conditional expressions: (1) 14.0 lt; vd (RN) lt; 19.6, 19.6; (2) 18.0 lt; vd (RN) lt; 23.3, 23.3; (3) 380 lt; vd (RN) / (ng-nF) lt; 1080, 1080; (4) vd (RP) + vd (RN) lt; 79); (5) f1 / flt; -1.1,...,-1.1; (6) f2 / flt; -2.2,-2.2; (7) 1.92 lt; f < 2 > is 6 / f < lt >; 3; the effect of inhibiting magnification chromatic aberration is achieved, the requirement for a large clear range can be met, and confocal of white light and fluorescent light is achieved; meanwhile, optical shooting guarantee is provided for the paranasal sinus endoscopic medical imaging technology, the completeness and authenticity of optical data are guaranteed, and the effectiveness of the optical data is improved for imaging medical treatment and remote medical treatment.

Description

Technical Field

[0001] The invention relates to an objective lens optical system for a sinus endoscope. Background Art

[0002] An endoscope is a detection instrument that consists of a thin tube with a light device that enters the interior of the object to be inspected and observed. It displays the internal image of the object through image sensors, optical lenses and electronic equipment. It integrates traditional optics, ergonomics, precision machinery, modern electronics, digital software and other technologies.

[0003] The emergence of elastic soft endoscopes has brought great convenience to medical technology. The special elasticity and twistability of soft materials can enable the endoscope lens to rotate in multiple directions for observation. With the help of endoscopes, doctors can see lesions that are invisible to X-rays and perform operations such as lighting, surgery, flushing and diagnosis. It is currently used in many applications such as gastroscopy, colonoscopy, laryngoscope, hysteroscopy, etc.

[0004] In the medical field, a sinus endoscope is used to examine biological tissues inside the human body. A sinus endoscope system includes: a sinus endoscope provided with an imaging element and having an insertion portion that can be inserted into a subject, and an image processing device connected to the sinus endoscope via a cable, performing image processing on an in-vivo image corresponding to an imaging signal generated by the imaging element, and displaying the in-vivo image on a display screen.

[0005] CN201710125040.2 "Endoscopic imaging objective optical system" comprises, from the object side to the image side, a first lens with negative focal power, an aperture and a second lens with positive focal power, satisfying the following conditional formulas: f / H(L1r1)﹤2.8; H(L1r1) / IMH﹤0.6; TTL / f﹤4; BF / f﹥1.5; wherein, f is the focal length of the endoscopic imaging objective optical system, H(L1r1) refers to the height corresponding to the main light corresponding to the maximum image height during normal observation passing through the object side surface of the first lens group, IMH is the maximum image height on the chip photosensitive surface corresponding to normal observation, TTL is the distance from the object side surface of the first lens on the optical axis to the chip photosensitive surface, and BF is the distance from the image side of the second lens on the optical axis to the chip photosensitive surface; it has the characteristics of wide field of view and compact structure.

[0006] An objective optical system for an endoscope includes, from the object side, a front group having negative refractive power as a whole; an opening aperture; and a rear group having positive refractive power as a whole, wherein the front group includes, from the object side, a first lens having negative refractive power, the absolute value of the curvature radius of the lens surface on the image side being smaller than the absolute value of the curvature radius of the lens surface on the object side; and at least one parallel plane component whose incident surface and exit surface are perpendicular to the optical axis, and the rear group includes, from the object side, a second lens having positive refractive power; a third lens having negative refractive power; and a fourth lens having positive refractive power, wherein the third lens and the fourth lens are bonded to form a bonded lens, the concave surface of the bonded surface of the bonded lens faces the image side, and satisfies the following conditional formula (1). 0.02<f / fc<0.10(1) wherein f is the focal length of the entire system; fc is the focal length of the bonded lens; an objective optical system for an endoscope having a wide angle, reduced distortion and phase difference, and capable of achieving good optical performance is provided.

[0007] CN206321872U discloses an endoscopic imaging objective optical system, which includes, from the object side to the image side, a first lens with negative focal power, an aperture and a second lens with positive focal power, satisfying the following conditional formulas: f / H(L1r1)﹤2.8; H(L1r1) / IMH﹤0.6; TTL / f﹤4; BF / f﹥1.5; wherein: f is the focal length of the endoscopic imaging objective optical system, H(L1r1) refers to the height corresponding to the main light corresponding to the maximum image height during normal observation passing through the surface on the object side of the first lens group, IMH is the maximum image height on the chip photosensitive surface corresponding to normal observation, TTL is the distance from the object side of the first lens on the optical axis to the chip photosensitive surface, and BF is the distance from the image side of the second lens on the optical axis to the chip photosensitive surface. The system has the characteristics of wide field of view and compact structure.

[0008] As a sinus endoscope in medical examination, high definition is the primary element to ensure the accuracy of medical examination. In the past, sinus endoscopes were basically 2K standard, which made it difficult to achieve high-definition examination. When using sinus endoscopes for diagnosis in the body cavity, if the chromatic aberration of the objective optical system of the sinus endoscope is not fully corrected, it is difficult to see the lesions with color bleeding in the peripheral part; since the white light and fluorescence focusing distances of sinus endoscopes are different, repeated focusing is required for clear observation, which is very inconvenient and affects medical efficiency. The clarity of existing sinus endoscopes is basically 2k, and the clarity of existing sinus endoscopes in 4K is basically white light. The existing 4K sinus endoscopes have large white light and fluorescence focusing deviations and cannot be observed at the same time. Summary of the invention

[0009] The object of the present invention is to provide an objective optical system for a sinus endoscope, which has the function of suppressing the occurrence of magnification chromatic aberration, can meet a large clear range, and realize the confocal of white light and fluorescence.

[0010] To achieve the above-mentioned object, the objective optical system for a sinus endoscope of the present invention comprises, from the object side, a first lens group having negative optical power, a second lens group having positive optical power, an aperture, a third lens group having negative optical power, and a fourth lens group having positive optical power, wherein the first lens group is formed by two groups of negative single lenses cemented together from the object side; the second lens group is formed by a flat plate and a positive single lens cemented together from the object side; the third lens group is formed by a negative single lens and a cemented lens having positive optical power formed by cementing a positive lens and a negative lens together from the object side; the fourth lens group is formed by two groups of positive single lenses from the object side, and satisfies the following conditional formula: (1) 14.0 <vd(RN)<19.6; Wherein: vd(RN) is the Abbe number of the negative lens in the lens of the first lens group under the d-line, and the d-line is yellow light.

[0011] (2) 18.0 <vd(RN)<23.3; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0012] (3) 380 <vd(RN) / (ng-nF)<1080; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

[0013] (4) vd(RP)+vd(RN)<79; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0014] (5) f1 / f<-1.1; Wherein: f1 is the focal length of lens L1 in the first lens group, and f is the composite focal length of the entire lens system, i.e., L1 to L9.

[0015] (6) f2 / f<-2.2; Among them: f2 is the focal length of lens L2 in the first lens group, and f is the composite focal length of the entire lens system, namely L1 to L9.

[0016] (7) 1.92 <f2-6 / f<3; Among them: f2-6 is the composite focal length of the other lenses after removing only the lens arranged closest to the object side, that is, the composite focal length of lenses L2 to L6, and f is the composite focal length of the entire lens system, that is, L1 to L9.

[0017] In a further preferred embodiment, the lens L2 of the first lens group satisfies the conditional formula (8): 380 <vd(RN) / (ng-nF)<600。

[0018] Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

[0019] In a further preferred embodiment, the lens L2 of the first lens group satisfies the conditional formula (9): 397 <vd(RN) / (ng-nF)<515。

[0020] Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

[0021] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy conditional formula (10): vd(RP)+vd(RN)<79.

[0022] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0023] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy conditional formula (11): 71 <vd(RP)+vd(RN)<79.9。

[0024] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0025] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group further satisfy conditional formula (12): 75 <vd(RP)+vd(RN)<78.5。

[0026] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0027] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy the conditional formula (13): 41.5 <vd(RP)-vd(RN)。

[0028] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0029] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy the condition (14): 41.3 <vd(RP)-vd(RN)<45.5。

[0030] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0031] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy the conditional formula (15): 41.0 <vd(RP)-vd(RN)<44.1。

[0032] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0033] FMC film is coated on lens L1 and lens L2, phase film is coated on lens L3, and AL2O3 is coated on lens L6 and lens L7; The first lens group is composed of a negative lens L1 and a negative lens L2. The negative lens L1 is a meniscus lens, i.e., one side is a concave transparent surface and the other side is a convex transparent surface. Both sides of the negative lens L2 are concave transparent surfaces. The concave transparent surface of the negative lens L1 is correspondingly bonded to any side of the negative lens L2 to form the first lens group. The second lens group is composed of a flat mirror L3 and a positive lens L4. The flat mirror L3 is a flat mirror with both sides being flat. The positive lens L4 is a convex lens with one side being convex and the other side being flat. Any side of the flat mirror L3 is bonded to the flat surface of the positive lens L4 to form the second lens group. The third lens group is composed of a negative lens L5, a lens L6 and a lens L7. The lens L6 and the lens L7 are each composed of a biconvex mirror and a biconcave mirror. The convex surface of the biconvex mirror and the concave surface of the biconcave mirror are bonded to form the lens L6 and the lens L7. The concave surface of the lens L5 is bonded to the concave surface of the lens L6. The convex surfaces of the lens L6 and the lens L7 correspond to each other. The fourth lens group is composed of lens L8 and lens L9. Lens L8 is a double convex lens, and lens L9 is a concave-convex lens with one side being convex and the other side being concave. The two convex surfaces of lens L8 are arranged corresponding to the concave surface of lens L7 and the convex surface of lens L9 respectively.

[0034] The aperture stop is provided between lens L4 and lens L5.

[0035] Lenses L1 and L2 of the first lens group, lenses L3 and L4 of the second lens group, an aperture, lenses L5, L6 and L7 of the third lens group, and lenses L8 and L9 of the fourth lens group are placed in corresponding positions in the lens barrel according to the order of arrangement and combination.

[0036] The objective optical system for a sinus endoscope of the present invention has the following excellent effects compared with the prior art.

[0037] The objective optical system for the sinus endoscope of the present invention adopts negative lenses L1 and L2. Among the high-dispersion lens materials, the material with the lowest Abbe number can be selected for optimal design. By applying negative optical focal length to the bonding lens configured by the first lens group to expand the field of view, it is possible to correct the magnification chromatic aberration well while realizing a wide field of view; lens L3 is a flat mirror without focal length, and a low refractive index material is selected to meet the need for compensating chromatic aberration; lenses L6 and L7 are used to effectively adjust the elimination of chromatic aberration and better correct chromatic aberration; lenses L8 and L9 use ED glass, which effectively eliminates full-spectrum chromatic aberration and secondary chromatic aberration in the ultra-wide wavelength range of 400nm-900nm, reduces chromatic aberration changes, and at the same time controls the focal length position of white light and fluorescence to remain unchanged, thereby realizing confocality of white light and fluorescence.

[0038] The arrangement and combination design of lenses L1 to L9 in the present invention is ingenious, compact and reasonable, and different materials are selected. When the conditional formula is met, the confocality of white light and fluorescence is achieved, the fluorescent white light is focused without deviation, the focusing operation is in place at one time, and a wide field of view is achieved. The clarity of white light and fluorescence can reach 4K imaging standards. The aperture is set between lens L4 and lens L5 to meet the requirements of large aperture and high transmittance. The use of ED materials ensures that the ultra-high-definition large aperture white light fluorescence confocality and full-spectrum design can effectively eliminate edge chromatic aberration. The use of FMC coating technology and prism phase film technology effectively solves the control of stray light and improvement of contrast in large aperture and full spectrum conditions.

[0039] By adopting the arrangement and combination design of lenses L1 to L9 in the present invention, when the conditional formula is met, the full-spectrum (400nm-900nm) spectral chromatic aberration is effectively eliminated, reducing or avoiding the misjudgment of the cell blood vessel edges during surgery; the white light and fluorescence are used at the same time, and in addition to providing the surface image of the human tissue, the fluorescent development of the tissue below the surface can also be realized; it can meet the clinical needs of traditional white light sinus endoscopes, and can also meet the needs of fluorescent field surgery with higher requirements for lesion identification ability, effectively reducing the equipment configuration of the operating room and improving the diagnosis and treatment capabilities of hospital departments.

[0040] The use of FMC coating and phase film technology can effectively reduce and avoid the problems of ghost images, virtual images, and stray light in sinus endoscope images that affect surgical accuracy, effectively avoid or reduce surgical misjudgments, and enhance surgical diagnosis and treatment capabilities. At the same time, it provides optical camera guarantees for sinus endoscopy medical imaging technology, ensures the integrity and authenticity of optical data, and improves the effectiveness of optical data for imaging medicine and telemedicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the optical system of the present invention.

[0042] Figure 2 A schematic diagram of light.

[0043] Figure 3 This is a schematic diagram of MTF white light.

[0044] Figure 4 Schematic diagram of MTF fluorescence.

[0045] Figure 5 Schematic diagram of axial chromatic aberration.

[0046] Figure 6 Schematic diagram of edge chromatic aberration.

[0047] Figure 7 Schematic diagram of field curvature curve.

[0048] Figure 8 Schematic diagram of the distortion curve.

[0049] in: Figure 3 In the MTF white light diagram, the horizontal axis is the modulation transfer function frequency, unit LP / MM, and the vertical axis is the modulation transfer function amplitude, no unit; Figure 4 In the MTF fluorescence diagram, the horizontal axis is the modulation transfer function frequency, unit LP / MM, and the vertical axis is the modulation transfer function amplitude, no unit; Figure 5 In the schematic diagram of axial chromatic aberration, the horizontal axis is focus shift, unit: micrometer μm, and the vertical axis is wavelength, unit: micrometer μm; Figure 6In the edge color difference diagram, the horizontal axis is color difference, unit: micrometer μm, and the vertical axis is field angle, unit: degree; Figure 7 In the field curvature diagram, the horizontal axis is the offset, unit: micrometer μm, and the vertical axis is the normalized field of view, no unit; Figure 8 In the distortion curve diagram, the horizontal axis is the offset percentage, unit: %, and the vertical axis is the normalized field of view, no unit. DETAILED DESCRIPTION

[0050] The objective optical system for the sinus endoscope of the present invention will be further described in detail below with reference to the accompanying drawings.

[0051] Figure 1 The objective optical system for a sinus endoscope shown in the figure includes, from the object side, a first lens group with negative optical power, a second lens group with positive optical power, an aperture, a third lens group with negative optical power, and a fourth lens group with positive optical power. The first lens group is composed of two groups of negative single lenses cemented together from the object side; the second lens group is composed of a flat plate and a positive single lens cemented together from the object side; the third lens group is composed of a negative single lens and a cemented lens with positive optical power formed by cementing a positive lens and a negative lens together from the object side; the fourth lens group is composed of two groups of positive single lenses from the object side, and satisfies the following conditional formula: (1) 14.0 <vd(RN)<19.6; Wherein: vd(RN) is the Abbe number of the negative lens in the lens of the first lens group under the d-line, and the d-line is yellow light.

[0052] (2) 18.0 <vd(RN)<23.3; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0053] (3) 380 <vd(RN) / (ng-nF)<1080; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

[0054] (4) vd(RP)+vd(RN)<79; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0055] (5) f1 / f<-1.1; Wherein: f1 is the focal length of lens L1 in the first lens group, and f is the composite focal length of the entire lens system, i.e., L1 to L9.

[0056] (6) f2 / f<-2.2; Among them: f2 is the focal length of lens L2 in the first lens group, and f is the composite focal length of the entire lens system, namely L1 to L9.

[0057] (7) 1.92 <f2-6 / f<3; Among them: f2-6 is the composite focal length of the other lenses after removing only the lens arranged closest to the object side, that is, the composite focal length of lenses L2 to L6, and f is the composite focal length of the entire lens system, that is, L1 to L9.

[0058] In a further preferred embodiment, the lens L2 of the first lens group satisfies the conditional formula (8): 380 <vd(RN) / (ng-nF)<600。

[0059] Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

[0060] In a further preferred embodiment, the lens L2 of the first lens group satisfies the conditional formula (9): 397 <vd(RN) / (ng-nF)<515。

[0061] Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

[0062] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy conditional formula (10): vd(RP)+vd(RN)<79.

[0063] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0064] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy conditional formula (11): 71 <vd(RP)+vd(RN)<79.9。

[0065] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0066] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy conditional formula (12): 75 <vd(RP)+vd(RN)<78.5。

[0067] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0068] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy the conditional formula (13): 41.5 <vd(RP)-vd(RN)。

[0069] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0070] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy the condition (14): 41.3 <vd(RP)-vd(RN)<45.5。

[0071] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0072] In a further preferred embodiment, the lens L1 and the lens L2 of the first lens group satisfy the conditional formula (15): 41.0 <vd(RP)-vd(RN)<44.1。

[0073] Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

[0074] FMC film is coated on lens L1 and lens L2, phase film is coated on lens L3, and AL2O3 is coated on lens L6 and lens L7; The first lens group is composed of a negative lens L1 and a negative lens L2. The negative lens L1 is a meniscus lens, i.e., one side is a concave transparent surface and the other side is a convex transparent surface. Both sides of the negative lens L2 are concave transparent surfaces. The concave transparent surface of the negative lens L1 is correspondingly bonded to any side of the negative lens L2 to form the first lens group. The second lens group is composed of a flat mirror L3 and a positive lens L4. The flat mirror L3 is a flat mirror with both sides being flat. The positive lens L4 is a convex lens with one side being convex and the other side being flat. Any side of the flat mirror L3 is bonded to the flat surface of the positive lens L4 to form the second lens group. The third lens group is composed of a negative lens L5, a lens L6 and a lens L7. The lens L6 and the lens L7 are each composed of a biconvex mirror and a biconcave mirror. The convex surface of the biconvex mirror and the concave surface of the biconcave mirror are bonded to form the lens L6 and the lens L7. The concave surface of the lens L5 is bonded to the concave surface of the lens L6. The convex surfaces of the lens L6 and the lens L7 correspond to each other. The fourth lens group is composed of lens L8 and lens L9. Lens L8 is a double convex lens, and lens L9 is a concave-convex lens with one side being convex and the other side being concave. The two convex surfaces of lens L8 are arranged corresponding to the concave surface of lens L7 and the convex surface of lens L9 respectively.

[0075] The aperture stop is provided between lens L4 and lens L5.

[0076] The lens L1 and lens L2 of the first lens group are bonded to the lens L3 and lens L4 of the second lens group by adhesive, and the aperture is kept at a certain distance from the lens L4 and lens L5 respectively, and then placed in the lens barrel. The lens L5 and lens L6 of the third lens group are placed in the lens barrel according to the arrangement requirements, and a spacer is provided between the lens L6 and the lens L7. The spacer is bonded to the lens L6 and the lens L7 respectively and placed in the lens barrel. A spacer is also provided between the lens L8 and the lens L9 of the fourth lens group, and they are respectively placed in corresponding positions in the lens barrel according to the arrangement and combination sequence and fixed by adhesive.

[0077] After the light passes through lens L1 and lens L2, the beam diameter becomes smaller and enters the bonded lens of lens L3 and lens L4; lens L1 and lens L2 can effectively control the light diameter to reduce the influence of aberration; after being diverged by lens L3 and lens L4, it enters lens L5, lens L6, and lens L7 for the first image, ensuring smooth transmission of light, and the first image is converged by lens L8 and lens L9 for secondary image.

[0078] In order to further eliminate full-spectrum chromatic aberration and secondary chromatic aberration, lens L8 and lens L9 use ED glass to reduce the chromatic aberration variation in the ultra-wide wavelength of 400nm-900nm, while controlling the focus position of white light and fluorescence to remain unchanged.

[0079] Lens L6 and lens L7 are composed of a positive lens and a negative lens, which can be adjusted to achromatically and can correct chromatic aberration well.

Claims

1. An objective optical system for a sinus endoscope, comprising, from the object side, a first lens group having negative power, a second lens group having positive power, an aperture, a third lens group having negative power, and a fourth lens group having positive power, characterized in that The first lens group is composed of two groups of negative single lenses cemented together in order from the object side; the second lens group is composed of a flat plate and a positive single lens cemented together in order from the object side; the third lens group is composed of a negative single lens and a cemented lens with positive power formed by cementing a positive lens and a negative lens in order from the object side; the fourth lens group is composed of two groups of positive single lenses in order from the object side, and satisfies the following conditional formula: (1) 14.0 <vd(RN)<19.6; Where: vd(RN) is the Abbe number of the negative lens in the first lens group under the d-line, and the d-line is yellow light; (2) 18.0 <vd(RN)<23.3; Where: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light; (3) 380 <vd(RN) / (ng-nF)<1080; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm; (4) vd(RP)+vd(RN)<79; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light; (5) f1 / f<-1.1; Where: f1 is the focal length of lens L1 in the first lens group, and f is the composite focal length of the entire lens system, i.e., L1 to L9; (6) f2 / f<-2.2; Where: f2 is the focal length of lens L2 in the first lens group, and f is the composite focal length of the entire lens system, i.e., L1 to L9; (7) 1.92 <f2-6 / f<3; Among them: f2-6 is the composite focal length of the other lenses after removing only the lens arranged closest to the object side, that is, the composite focal length of lenses L2 to L6, and f is the composite focal length of the entire lens system, that is, L1 to L9.

2. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L2 of the first lens group satisfies conditional formula (8): 380 <vd(RN) / (ng-nF)<600; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

3. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L2 of the first lens group satisfies conditional formula (9): 397 <vd(RN) / (ng-nF)<515; Wherein: vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, the d-line is yellow light, ng is the refractive index of the negative lens in the cemented lens of the third lens group for the g-line, the g-line is blue light with a wavelength of 435.84nm, nF is the refractive index of the negative lens in the cemented lens of the third lens group for the F-line, the F-line is cyan light with a wavelength of 486.13nm.

4. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L1 and the lens L2 of the first lens group satisfy the conditional formula (10): vd(RP)+vd(RN)<79; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

5. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L1 and the lens L2 of the first lens group satisfy the conditional formula (11): 71 <vd(RP)+vd(RN)<79.9; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

6. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L1 and the lens L2 of the first lens group satisfy conditional formula (12): 75 <vd(RP)+vd(RN)<78.5; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

7. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L1 and the lens L2 of the first lens group satisfy conditional formula (13): 41.5 <vd(RP)-vd(RN); Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

8. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L1 and the lens L2 of the first lens group satisfy conditional formula (14): 41.3 <vd(RP)-vd(RN)<45.5; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

9. The objective optical system for a sinus endoscope according to claim 1, characterized in that The lens L1 and the lens L2 of the first lens group satisfy the conditional formula (15): 41.0 <vd(RP)-vd(RN)<44.1; Wherein: vd(RP) is the Abbe number of the positive lens in the cemented lens of the third lens group under the d-line, vd(RN) is the Abbe number of the negative lens in the cemented lens of the third lens group under the d-line, and the d-line is yellow light.

10. The objective optical system for a sinus endoscope according to claim 1, characterized in that The first lens group is composed of a negative lens L1 and a negative lens L2. The negative lens L1 is a concave-convex lens, that is, one side is a concave transparent surface and the other side is a convex transparent surface. Both sides of the negative lens L2 are concave transparent surfaces. The concave transparent surface of the negative lens L1 is bonded to any side of the negative lens L2 to form the first lens group. The second lens group is composed of a flat mirror L3 and a positive lens L4. The flat mirror L3 is a flat mirror with both sides being flat. The positive lens L4 is a convex lens with one side being a convex surface and the other side being flat. Any side of the flat mirror L3 is bonded to the flat surface of the positive lens L4 to form the second lens group. The third lens The group is composed of negative lens L5, lens L6 and lens L7. Lens L6 and lens L7 are both composed of a double convex mirror and a double concave mirror. The convex surface of the double convex mirror is bonded to the concave surface of the double concave mirror to form lens L6 and lens L7. The concave surface of lens L5 is bonded to the concave surface of lens L6, and the convex surfaces of lens L6 and lens L7 correspond to each other. The fourth lens group is composed of lens L8 and lens L9. Lens L8 is a double convex mirror, and lens L9 is a concave-convex mirror, one side is convex and the other side is concave. The two convex surfaces of lens L8 are arranged corresponding to the concave surface of lens L7 and the convex surface of lens L9 respectively.

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