Large-aperture low-distortion objective optical system based on 16mm image intensifier

Abstract

The invention provides a large-aperture low-distortion objective optical system based on a 16mm image intensifier, belongs to the technical field of optical imaging, and is used for solving the problems that an optical system of the 16mm image intensifier is poor in imaging quality and high in cost. The optical system comprises a diaphragm, and a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged from an object plane to an image plane along an optical axis. The first to sixth lenses are glass spherical lenses. The seventh lens is a plastic aspheric lens. The diaphragm is located between the third lens and the fourth lens. The fifth lens has negative focal power, the fifth lens and the fourth lens are glued together, and the image side of the fifth lens is a concave surface. The optical system can be suitable for imaging scenes under low illumination, and meets the requirements of a large view field, a large aperture, high transmittance, low distortion and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of optical imaging, and in particular relates to a large-aperture, low-distortion objective optical system based on a 16mm image intensifier. Background Art

[0002] With the development of optical imaging technology, the demand for high-resolution optical systems in the field of low-light detection has surged. Compared with 18mm image intensifiers, 16mm image intensifiers are lighter and smaller in size. Therefore, 16mm image intensifiers have advantages in applications that are sensitive to weight and size. There are currently few optical objective lenses suitable for 16mm image intensifiers, and traditional glass spherical objective lenses have difficulty correcting wide-band chromatic aberration. Although the addition of glass aspherical objective lenses can stabilize the imaging quality, the cost of glass aspherical surfaces is relatively high. Compared with optical glass materials, optical plastics have the advantages of low manufacturing cost, light weight, and the ability to be designed into complex surface shapes. However, their transmittance is low and they do not have the low-light advantage. In addition, their expansion coefficient is relatively large, making it difficult to meet the imaging requirements of a large temperature range and placing high demands on assembly. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to provide a large-aperture, low-distortion objective optical system based on a 16mm image intensifier, which can be used for imaging scenes under low illumination and meet the requirements of a larger field of view, a larger aperture, a higher transmittance, a lower distortion and a low cost.

[0004] To address the above-mentioned issues, the present invention provides a large-aperture, low-distortion objective optical system based on a 16mm image intensifier, comprising an aperture and a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane. The first through sixth lenses are glass spherical lenses. The seventh lens is a plastic aspherical lens. The aperture is located between the third and fourth lenses.

[0005] The first lens has positive refractive power, a convex object side surface and a concave image side surface.

[0006] The second lens has negative refractive power, and its object side surface is concave and its image side surface is concave.

[0007] The third lens has positive refractive power, with a convex object side surface and a convex image side surface.

[0008] The fourth lens has positive refractive power, and its object side surface is convex and its image side surface is convex.

[0009] The fifth lens has negative refractive power, is cemented together with the fourth lens, and has a concave image side.

[0010] The sixth lens has positive refractive power, with a convex object side surface and a convex image side surface.

[0011] The seventh lens has negative refractive power, and its object side surface and image side surface are concave.

[0012] Among them, the first lens satisfies:

[0013] 3≥|fA1 / ΦA1|≥2, and Nd1≥1.9, Vd1≥30, 33mm <fA1<34mm。

[0014] Where fA1 is the focal length of the first lens. ΦA1 is the effective aperture of the first lens. Nd1 is the refractive index of the first lens. Vd1 is the Abbe number of the first lens.

[0015] Among them, the second lens satisfies:

[0016] 2≥|fA2 / ΦA2|≥1, and Nd2≥1.75, Vd2≥20, -17mm <fA2<-16mm。

[0017] Where fA2 is the focal length of the second lens. ΦA2 is the effective aperture of the second lens. Nd2 is the refractive index of the second lens. Vd2 is the Abbe number of the second lens.

[0018] Among them, the third lens satisfies:

[0019] 2≥|fA3 / ΦA3|≥1, and Nd3≥1.95, Vd3≥30, 21mm <fA3<22mm。

[0020] Where fA3 is the focal length of the third lens. ΦA3 is the effective aperture of the third lens. Nd3 is the refractive index of the third lens. Vd3 is the Abbe number of the third lens.

[0021] Among them, the fourth lens satisfies:

[0022] 1≥|fC1 / ΦC1|≥0.5, and Nd4≥1.9. Vd4≥35, 14mm <fC1<15mm。

[0023] Where, fC1 is the focal length of the fourth lens. ΦC1 is the effective aperture of the fourth lens. Nd4 is the refractive index of the fourth lens. Vd4 is the Abbe number of the fourth lens.

[0024] Among them, the fifth lens satisfies:

[0025] 1≥|fC2 / ΦC2|≥0.5, and Nd5≥1.9, Vd5≤20, -12mm <fC2<-11mm。

[0026] Wherein, fC2 is the focal length of the fifth lens, ΦC2 is the effective aperture of the fifth lens, Nd5 is the refractive index of the fifth lens, and Vd5 is the Abbe number of the fifth lens.

[0027] Among them, the sixth lens satisfies:

[0028] 2≥|fC3 / ΦC3|≥1, and Nd6≥2.0, Vd6≥25, 13mm <fC3<14mm。

[0029] Wherein, fC3 is the focal length of the sixth lens, ΦC3 is the effective aperture of the sixth lens, Nd6 is the refractive index of the sixth lens, and Vd6 is the Abbe number of the sixth lens.

[0030] Among them, the seventh lens satisfies:

[0031] 3≥|fC4 / ΦC4|≥2, and Nd7≥1.60, Vd7≥23, -26mm <fC4<-27mm。

[0032] Wherein, fC4 is the focal length of the seventh lens, ΦC4 is the effective aperture of the seventh lens, Nd7 is the refractive index of the seventh lens, and Vd7 is the Abbe number of the seventh lens.

[0033] Among them, the optical system meets the following requirements:

[0034] f / L≥0.5.

[0035] Where f is the focal length of the optical system and L is the total optical length.

[0036] The first, third, fourth, and sixth lenses are made of heavy lanthanum flint glass. The second and fifth lenses are made of flint glass. The seventh lens is made of optical resin polymer.

[0037] Beneficial effects:

[0038] The large-aperture, low-distortion objective optical system based on a 16mm image intensifier provided by the present invention has a first lens to a sixth lens made of glass spherical lenses, which have a high refractive index and can correct aberrations; the seventh lens is made of a plastic aspherical lens, which can correct the balance of field curvature and chromatic aberration of the objective lens. The optical system provided by the present invention adopts a glass-plastic hybrid design of six glass spherical lenses and one plastic aspherical lens, which is low in cost, simple to assemble and adjust, and easy to mass produce. It not only ensures transmittance but also achieves high-resolution imaging, and can have good imaging quality under extreme environments of -30°C to 50°C. The optical system provided by the present invention can achieve good correction of axial chromatic aberration and lateral chromatic aberration of the entire optical system through material matching and lens optical power distribution, and can effectively correct the high-order aberrations of the entire optical system through surface design, so that the incident angle of light on each mirror surface is small, and the overall imaging quality of the system is excellent. The optical system provided by the present invention combines the low-light response characteristics of a 16mm image intensifier to achieve the goals of a large field of view (2ω≥40°), a large aperture (F#≤1.1), high transmittance (≥85%), wide-band achromatism (λ=500nm~900nm), and low distortion (optical distortion ≤0.5%). BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of a large-aperture, low-distortion objective optical system based on a 16mm image intensifier according to an embodiment of the present invention;

[0040] Figure 2 A diagram showing the light propagation path of a large-aperture, low-distortion objective optical system based on a 16mm image intensifier according to an embodiment of the present invention;

[0041] Figure 3 An optical point diagram of a large-aperture, low-distortion objective optical system based on a 16mm image intensifier according to an embodiment of the present invention;

[0042] Figure 4 A schematic diagram of optical field curvature and distortion of a large-aperture, low-distortion objective optical system based on a 16mm image intensifier according to an embodiment of the present invention;

[0043] Figure 5 This is an optical transfer function diagram of a large-aperture, low-distortion objective optical system based on a 16mm image intensifier according to an embodiment of the present invention.

[0044] The reference numerals indicate:

[0045] A1, first lens; A2, second lens; A3, third lens; B, aperture; C1, fourth lens; C2, fifth lens; C3, sixth lens; C4, seventh lens;

[0046] S1 is the object side of the first lens; S2 is the image side of the first lens;

[0047] S3 is the object-side surface of the second lens; S4 is the image-side surface of the second lens;

[0048] S5 is the object-side surface of the third lens; S6 is the image-side surface of the third lens;

[0049] STO is the aperture surface;

[0050] S8 is the object-side surface of the fourth lens; S9 is the image-side surface of the fourth lens;

[0051] S10 is the image-side surface of the fifth lens;

[0052] S11 is the object-side surface of the sixth lens; S12 is the image-side surface of the sixth lens;

[0053] S13 is the object-side surface of the seventh lens; S14 is the image-side surface of the seventh lens. DETAILED DESCRIPTION

[0054] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0055] like Figure 1 As shown, this embodiment provides a large-aperture, low-distortion objective optical system based on a 16mm image intensifier, comprising: an aperture B and a first lens A1, a second lens A2, a third lens A3, a fourth lens C1, a fifth lens C2, a sixth lens C3, and a seventh lens C4, which are arranged in sequence along the optical axis from the object plane to the image plane. The first lens A1 to the sixth lens C3 are glass spherical lenses. The seventh lens C4 is a plastic aspherical lens. The aperture B is located between the third lens A3 and the fourth lens C1. The first lens A1 has positive focal power, with a convex object side and a concave image side. The second lens A2 has negative focal power, with a concave object side and a concave image side. The third lens A3 has positive focal power, with a convex object side and a convex image side. The fourth lens C1 has positive focal power, with a convex object side and a convex image side. The fifth lens element C2 has negative refractive power and is cemented with the fourth lens element C1. The image side of the fifth lens element C2 is concave. The sixth lens element C3 has positive refractive power, with a convex object-side surface and a convex image-side surface. The seventh lens element C4 has negative refractive power, with a concave object-side surface and a concave image-side surface.

[0056] The large-aperture and low-distortion objective optical system based on a 16mm image intensifier in this embodiment. The first lens A1 to the sixth lens C3 use glass spherical lenses, which have a relatively high refractive index and can correct aberrations. The seventh lens C4 uses a plastic aspherical lens, which can correct the balance of the field curvature and chromatic aberration of the objective lens. The optical system of this embodiment adopts a hybrid design of six glass spherical lenses and one plastic aspherical lens, which has a lower cost, simple assembly and adjustment, is convenient for mass production, not only ensures the transmittance but also realizes high-resolution imaging, and can have good imaging quality in the extreme environment of -30°C to 50°C. The optical system of this embodiment effectively corrects the axial chromatic aberration and lateral chromatic aberration of the entire optical system through material matching and lens power distribution, and effectively corrects the high-order aberrations of the entire optical system through surface design, so that the incident angle of light rays on each mirror surface is small and the overall imaging quality of the system is excellent. The optical system of this embodiment combines the low-light response characteristics of the 16mm image intensifier to achieve the goals of a large field of view (2ω≥40°), a large aperture (F#≤1.1), a high transmittance (≥85%), an achromatic wide band (λ = 500nm to 900nm), and a low distortion (optical distortion ≤ 0.5%).

[0057] The optical indicators achieved by the optical system of this embodiment are: a wavelength band of 500nm to 900nm, a maximum distortion not greater than 0.5%, a focal length of 20.5mm, an overall optical length ≤ 40mm, an F number of 1.1, an image plane size adapted to a 16mm image intensifier, a maximum field of view distortion of about 0, and a field of view range of 42.6°.

[0058] As Figure 1 shown, in this embodiment, the first lens A1 satisfies: 3≥∣fA1 / ΦA1∣≥2, and Nd1≥1.9, Vd1≥30, 33mm < fA1 < 34mm. Where, fA1 is the focal length of the first lens A1. ΦA1 is the effective aperture of the first lens A1. Nd1 is the refractive index of the first lens A1. Vd1 is the Abbe number of the first lens A1.

[0059] Specifically, the refractive index of the first lens A1 is 1.90 and the Abbe number is 37.1; the radius of curvature of its object side surface S1 is 20.8mm, the surface interval is 2.6mm, and the effective aperture is set to 19mm; the radius of curvature of the image side surface S2 is 49mm, the surface interval is 7.2, and the effective aperture is 19mm.

[0060] As Figure 1 shown, in this embodiment, the second lens A2 satisfies: 2≥∣fA2 / ΦA2∣≥1, and Nd2≥1.75, Vd2≥20, -17mm < fA2 < -16mm. Where, fA2 is the focal length of the second lens A2. ΦA2 is the effective aperture of the second lens A2. Nd2 is the refractive index of the second lens A2. Vd2 is the Abbe number of the second lens A2.

[0061] Specifically, the refractive index of the second lens A2 is 1.78, and the Abbe number is 25.7; the radius of curvature of its object side S3 is -26 mm, the surface interval is 1.1 mm, and the effective aperture is 16 mm; the radius of curvature of its image side S4 is 26 mm, the surface interval is 2.2, and the effective aperture is 16 mm.

[0062] As Figure 1 shown, in this embodiment, the third lens A3 satisfies: 2 ≥ ∣fA3 / ΦA3∣ ≥ 1, and Nd3 ≥ 1.95, Vd3 ≥ 30, 21 mm < fA3 < 22 mm. Where, fA3 is the focal length of the third lens A3. ΦA3 is the effective aperture of the third lens A3. Nd3 is the refractive index of the third lens A3. Vd3 is the Abbe number of the third lens A3.

[0063] Specifically, the refractive index of the third lens A3 is 1.95, and the Abbe number is 32.3; the radius of curvature of its object side S5 is 40 mm, the surface interval is 2.9 mm, and the effective aperture is 17 mm; the radius of curvature of its image side S6 is -40 mm, the surface interval is 0.1, and the effective aperture is 17 mm.

[0064] As Figure 1 shown, in this embodiment, the fourth lens C1 satisfies: 1 ≥ ∣fC1 / ΦC1∣ ≥ 0.5, and Nd4 ≥ 1.9. Vd4 ≥ 35, 14 mm < fC1 < 15 mm. Where, fC1 is the focal length of the fourth lens C1. ΦC1 is the effective aperture of the fourth lens C1. Nd4 is the refractive index of the fourth lens C1. Vd4 is the Abbe number of the fourth lens C1.

[0065] Specifically, the refractive index of the fourth lens C1 is 1.91, and the Abbe number is 35.2; the radius of curvature of its object side S8 is 17.6 mm, the surface interval is 0 mm, and the effective aperture is 16 mm; the radius of curvature of its image side S9 is -47.6 mm, the surface interval is 2.6, and the effective aperture is 15 mm.

[0066] As Figure 1 shown, in this embodiment, the fifth lens C2 satisfies: 1 ≥ ∣fC2 / ΦC2∣ ≥ 0.5, and Nd5 ≥ 1.9, Vd5 ≤ 20, -12 mm < fC2 < -11 mm. Where, fC2 is the focal length of the fifth lens C2. ΦC2 is the effective aperture of the fifth lens C2. Nd5 is the refractive index of the fifth lens C2. Vd5 is the Abbe number of the fifth lens C2. <www.

[0067] Specifically, the refractive index of the fifth lens C2 is 1.95 and the Abbe number is 18; the radius of curvature of its object side is -47.6 mm, the surface interval is 2.6 mm, and the effective aperture is 15 mm; the radius of curvature of the image side S10 is 15 mm, the surface interval is 1.4, and the effective aperture is 12 mm.

[0068] As Figure 1 shown, in this embodiment, the sixth lens C3 satisfies: 2 ≥ |fC3 / ΦC3| ≥ 1, and Nd6 ≥ 2.0, Vd6 ≥ 25, 13 mm < fC3 < 14 mm. Where, fC3 is the focal length of the sixth lens C3. ΦC3 is the effective aperture of the sixth lens C3. Nd6 is the refractive index of the sixth lens C3. Vd6 is the Abbe number of the sixth lens C3.

[0069] Specifically, the refractive index of the sixth lens C3 is 2.0 and the Abbe number is 29.1; the radius of curvature of its object side S11 is 18.4 mm, the surface interval is 4.8 mm, and the effective aperture is 14 mm; the radius of curvature of the image side S12 is -52 mm, the surface interval is 2.1 mm, and the effective aperture is 14 mm.

[0070] As Figure 1 shown, in this embodiment, the seventh lens C4 satisfies: 3 ≥ |fC4 / ΦC4| ≥ 2, and Nd7 ≥ 1.60, Vd7 ≥ 23, -26 mm < fC4 < -27 mm. Where, fC4 is the focal length of the seventh lens C4. ΦC4 is the effective aperture of the seventh lens C4. Nd7 is the refractive index of the seventh lens C4. Vd7 is the Abbe number of the seventh lens C4.

[0071] Specifically, the refractive index of the seventh lens C4 is 1.64 and the Abbe number is 23.5; the vertex radius of curvature of its object side S13 is 24.3 mm, the surface interval is 1.1 mm, and the effective aperture is 14 mm; the vertex radius of curvature of the image side S14 is 55.4 mm, the surface interval is 2.95 mm, and the effective aperture is 15 mm. Both of its two surfaces are aspherical, and the expression of the aspherical curve equation is:

[0072]

[0073] Where, h is the height; Z(h) is the sagitta, the distance from the vertex of the aspherical surface along the optical axis at the position of height h; c = 1 / r, r represents the radius of curvature of the lens surface; k is the conic coefficient; A, B, C, D, E are the high-order aspherical coefficients.

[0074] As Figure 1 shown, in this embodiment, the large-aperture and low-distortion objective optical system based on a 16 mm image intensifier satisfies: f / L ≥ 0.5. Where, f is the focal length of the optical system, and L is the total optical length.

[0075] In this embodiment, the first lens A1, the third lens A3, the fourth lens C1, and the sixth lens C3 are made of heavy lanthanum flint glass. The second lens A2 and the fifth lens C2 are made of flint glass. The seventh lens C4 is made of an optical resin polymer.

[0076] Specifically, the mirror surfaces of the first, second, third, and sixth lenses (A1, A2, A3, C1, C2, and C3) are all made of white glass, while the mirror surface of the seventh lens (C4) is made of optical plastic. All lenses are coated to the near-infrared band. Furthermore, the seventh lens (C4) utilizes EP6000, developed and produced by Mitsubishi Gas Chemical Co., Ltd. of Japan.

[0077] in, Figure 2 FIG. 1 is a diagram of the light propagation path of the large-aperture, low-distortion objective optical system based on the 16 mm image intensifier of this embodiment. Figure 3 1 is an optical point diagram of the large-aperture, low-distortion objective optical system based on a 16mm image intensifier in this embodiment. Figure 4 Schematic diagram of optical field curvature and distortion of the large-aperture, low-distortion objective optical system based on a 16mm image intensifier in this embodiment. Figure 5 Graph showing the optical transfer function of the large-aperture, low-distortion objective optical system based on a 16mm image intensifier in this embodiment.

[0078] Table 1 (Surface parameter values of each lens in this embodiment)

[0079]

[0080]

[0081] Table 2 (Aspheric coefficients of the seventh lens)

[0082]

[0083] Among them, k is the cone coefficient; B, C, D, and E are high-order aspheric coefficients, and the E in the coefficient represents the scientific symbol, such as E-004 represents 10-4.

[0084] As shown in Table 1, the refractive index Nd of first lens element A1 is 1.90, and its Abbe number Vd is 37.1. The radius of curvature of the object-side surface S1 of first lens element A1 is 20.8 mm, the surface spacing is 2.6 mm, and the effective aperture is 19 mm. The radius of curvature of the image-side surface S2 of first lens element A1 is 49 mm, the surface spacing is 7.2, and the effective aperture is 18 mm.

[0085] The refractive index Nd of the second lens element A2 is 1.78, and the Abbe number Vd is 25.7. The radius of curvature of the object-side surface S3 of the second lens element A2 is -26 mm, the surface spacing is 1.1 mm, and the effective aperture is 16 mm. The radius of curvature of the image-side surface S4 of the second lens element A2 is 26 mm, the surface spacing is 2.2 mm, and the effective aperture is 16 mm.

[0086] The refractive index Nd of the third lens element A3 is 1.95, and its Abbe number Vd is 32.3. The radius of curvature of the object-side surface S5 of the third lens element A3 is 40 mm, the surface spacing is 2.9 mm, and the effective aperture is 17 mm. The radius of curvature of the image-side surface S6 of the third lens element A3 is -40 mm, the surface spacing is 0.1 mm, and the effective aperture is 17 mm.

[0087] The STO interval on the aperture B surface is 0.1 mm and the effective aperture is 15.6 mm.

[0088] The refractive index Nd of the object-side surface S8 of the fourth lens element C1 is 1.91, and its Abbe number Vd is 35.2. The radius of curvature of the object-side surface S8 of the fourth lens element C1 is 17.6mm, the surface separation is 4.2mm, and the effective aperture is 15mm. The refractive index Nd of the image-side surface S9 of the fourth lens element C1 is 1.95, its Abbe number Vd is 18, its radius of curvature is -47.6mm, the surface separation is 2.6mm, and the effective aperture is 14mm.

[0089] The parameters of the object-side surface of the fifth lens element C2 are the same as those of the image-side surface S9 of the fourth lens element C1 . The radius of curvature of the image-side surface S10 is 15.0 mm, the surface spacing is 1.4 mm, and the effective aperture is 12 mm.

[0090] The refractive index Nd of the sixth lens element C3 is 2.0, and its Abbe number Vd is 25.5. The radius of curvature of the object-side surface S11 of the sixth lens element C3 is 18.4mm, the surface separation is 4.8mm, and the effective aperture is 14mm. The radius of curvature of the image-side surface S12 of the sixth lens element C3 is -52mm, the surface separation is 2.1mm, and the effective aperture is 14mm.

[0091] The refractive index Nd of the seventh lens element C4 is 1.64, and its Abbe number Vd is 23.5. The vertex radius of curvature of the object-side surface S13 of the seventh lens element C4 is -24.3 mm, the surface separation is 1.1 mm, and the effective aperture is 13 mm. The vertex radius of curvature of the image-side surface S14 of the seventh lens element C4 is 55.4 mm, the surface separation is 2.7 mm, and the effective aperture is 13 mm. Both surfaces of the seventh lens element C4 are aspherical. The aspherical coefficients of the seventh lens element C4 are shown in Table 2.

[0092] The protective glass of the image intensifier has a refractive index Nd of 1.52, an Abbe number Vd of 64.2, and a thickness of 3.9 mm.

[0093] This embodiment achieves complementary aberrations between the first lens A1, the second lens A2, and the third lens A3, and the fourth lens C1, the fifth lens C2, the sixth lens C3, and the seventh lens C4. The fourth lens C1 and the fifth lens C2 are cemented together to compensate for spherical and chromatic aberrations. Furthermore, the optical power of each lens is rationally calculated to meet the requirements for use in both high and low temperatures. This achieves high-definition image quality at an ultra-low cost, with a relatively large aperture and zero distortion. While maintaining high pixel quality during the day, it also maintains high-definition image quality at night or in low-light conditions. Furthermore, it remains usable in environments with varying temperatures.

[0094] This embodiment ensures balanced angles of incidence between the front and rear lens groups by rationally allocating lens refractive indices and focal powers, thus avoiding sensitive aberrations and reducing assembly and adjustment difficulties. By rationally allocating the focal lengths of the individual lenses, the imaging system's spherical aberration and field curvature are minimized, ensuring high imaging quality both on-axis and off-axis. This effectively addresses the problem of high distortion and poor imaging performance in existing large-aperture objective optical systems.

[0095] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0096] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention. The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and variations without departing from the technical principles of the present invention, and such improvements and variations shall also be considered within the scope of protection of the present invention.

Claims

1. A large-aperture, low-distortion objective optical system based on a 16mm image intensifier, characterized in that: The optical system comprises: an aperture and a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence along the optical axis from the object plane to the image plane; the first to sixth lenses are glass spherical lenses; the seventh lens is a plastic aspherical lens; the aperture is located between the third lens and the fourth lens; The first lens has positive optical power, a convex object side surface and a concave image side surface; The second lens has negative optical power, and its object side is concave and its image side is concave; The third lens has positive refractive power, and its object side is convex and its image side is convex; The fourth lens has positive refractive power, and its object side is convex and its image side is convex; The fifth lens has negative optical power, is cemented together with the fourth lens, and has a concave image side. The sixth lens has positive refractive power, and its object side is convex and its image side is convex; The seventh lens has negative refractive power, and its object side surface is concave and its image side surface is concave.

2. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The first lens satisfies: 3≥|fA1 / ΦA1|≥2, and Nd1≥1.9, Vd1≥30, 33mm <fA1<34mm; Wherein, fA1 is the focal length of the first lens; ΦA1 is the effective aperture of the first lens; Nd1 is the refractive index of the first lens; and Vd1 is the Abbe number of the first lens.

3. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The second lens satisfies: 2≥|fA2 / ΦA2|≥1, and Nd2≥1.75, Vd2≥20, -17mm <fA2<-16mm; Wherein, fA2 is the focal length of the second lens; ΦA2 is the effective aperture of the second lens; Nd2 is the refractive index of the second lens; and Vd2 is the Abbe number of the second lens.

4. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The third lens satisfies: 2≥|fA3 / ΦA3|≥1, and Nd3≥1.95, Vd3≥30, 21mm <fA3<22mm; Wherein, fA3 is the focal length of the third lens; ΦA3 is the effective aperture of the third lens; Nd3 is the refractive index of the third lens; and Vd3 is the Abbe number of the third lens.

5. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The fourth lens satisfies: 1≥|fC1 / ΦC1|≥0.5, and Nd4≥1.9; Vd4≥35, 14mm <fC1<15mm; Wherein, fC1 is the focal length of the fourth lens; ΦC1 is the effective aperture of the fourth lens; Nd4 is the refractive index of the fourth lens; and Vd4 is the Abbe number of the fourth lens.

6. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The fifth lens satisfies: 1≥|fC2 / ΦC2|≥0.5, and Nd5≥1.9, Vd5≤20, -12mm <fC2<-11mm; Wherein, fC2 is the focal length of the fifth lens; ΦC2 is the effective aperture of the fifth lens; Nd5 is the refractive index of the fifth lens; and Vd5 is the Abbe number of the fifth lens.

7. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The sixth lens satisfies: 2≥|fC3 / ΦC3|≥1, and Nd6≥2.0, Vd6≥25, 13mm <fC3<14mm; Wherein, fC3 is the focal length of the sixth lens; ΦC3 is the effective aperture of the sixth lens; Nd6 is the refractive index of the sixth lens; and Vd6 is the Abbe number of the sixth lens.

8. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The seventh lens satisfies: 3≥|fC4 / ΦC4|≥2, and Nd7≥1.60, Vd7≥23, -26mm <fC4<-27mm; Wherein, fC4 is the focal length of the seventh lens; ΦC4 is the effective aperture of the seventh lens; Nd7 is the refractive index of the seventh lens; and Vd7 is the Abbe number of the seventh lens.

9. The large-aperture, low-distortion objective optical system based on a 16 mm image intensifier according to claim 1, characterized in that: The optical system satisfies: f / L≥0.5; Where f is the focal length of the optical system and L is the total optical length.

10. The large-aperture, low-distortion objective optical system based on a 16mm image intensifier according to claim 1, characterized in that: The first lens, the third lens, the fourth lens and the sixth lens are made of heavy lanthanum flint glass; the second lens and the fifth lens are made of flint glass; and the seventh lens is made of optical resin polymer.

Images