Objective lens system and optical system

Abstract

The application discloses an objective lens system and an optical system. The objective lens system comprises: a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence from the object side to the image side along the optical axis direction of the objective lens system, the second lens and the third lens form a first doublet lens, and the fourth lens and the fifth lens form a second doublet lens; wherein the first lens has positive refractive power, the second lens has negative refractive power, the third lens has positive refractive power, the fourth lens has positive refractive power, the fifth lens has negative refractive power, and the sixth lens has negative refractive power. By adopting six lenses with specific structures arranged in sequence from the object side to the image side, and by specific distribution and combination of the refractive power of the six lenses, the micro-light night vision instrument using the objective lens system has a larger field of view and higher resolution in the full field of view.

Description

Technical Field

[0001] This application relates to the field of night vision objective lens technology, and in particular to an objective lens system and an optical system. Background Technology

[0002] The human eye has a limited spectral sensitivity and resolution, especially in low-light conditions at night, where its ability to recognize objects gradually deteriorates until it can no longer identify them. Low-light night vision devices, on the other hand, can amplify weak light by hundreds of thousands of times, making it visible to the naked eye. Operating in a passive mode, they can both observe targets and effectively conceal themselves, making them widely used in various fields.

[0003] To improve the observation performance of low-light night vision devices, they need to have higher resolution and a wider field of view. Among these, the objective lens of a low-light night vision device mainly determines its imaging resolution, distortion, light transmission, field of view, and weight. Furthermore, since the image is transmitted through an image intensifier, the objective lens needs to be independently corrected for aberrations. Summary of the Invention

[0004] This application provides at least one objective lens system and an optical system, so that a low-light night vision device using the objective lens system has a large field of view and high resolution across the entire field of view.

[0005] The first aspect of this application provides an objective lens system, which includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens arranged sequentially from the object side to the image side along the optical axis of the objective lens system. The second lens and the third lens form a first cemented doublet, and the fourth lens and the fifth lens form a second cemented doublet.

[0006] The first lens has positive optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has positive optical power, the fifth lens has negative optical power, and the sixth lens has negative optical power.

[0007] Optionally, the first lens and the sixth lens are aspherical mirrors.

[0008] Optionally, the objective lens system satisfies the following relationship:

[0009]

[0010] Where f1 is the focal length of the first lens; f is the focal length of the objective lens system.

[0011] Optionally, the total length of the objective lens system is 25.899 mm.

[0012] Optionally, the focal length of the objective lens system is 22.58 mm.

[0013] Optionally, the aperture F number of the objective lens system is 1.2.

[0014] Optionally, the objective lens system satisfies the following relationship:

[0015]

[0016] Wherein, f4 is the focal length of the fourth lens; f5 is the focal length of the fifth lens.

[0017] Optionally, the objective lens system satisfies the following relationship:

[0018] 1.8 < N < 1.95 d3 <1.95;

[0019] Wherein, N d3 is the refractive index of the third lens.

[0020] Optionally, the objective lens system satisfies the following relationship:

[0021] 30 < V < 50 d3 <50;

[0022] Wherein, V d3 is the Abbe number of the third lens.

[0023] The second aspect of the present application provides an optical system, which comprises the objective lens system as described above, an image intensifier and an ocular, the objective lens system is used to obtain the light generated by the target to be imaged, the light is processed by the image intensifier for amplification, and the image of the target to be imaged is formed on the image plane of the ocular.

[0024] The beneficial effects of the present application are: different from the prior art, the present application adopts six lenses with specific structures arranged in order from the object side to the image side, and the specific focal power distribution and combination of the six lenses are used to make the weight and size of the objective lens system small, so that the micro-light night vision device using the objective lens system has a larger field of view and has a higher resolution in the full field of view.

[0025] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, but not limiting the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 is a structural schematic diagram of an embodiment of the objective lens system of the present application;

[0028] Figure 2 is a curve diagram of the optical transfer function of the objective lens system of the present application;

[0029] Figure 3 is an analysis diagram of the chromatic spherical aberration of the objective lens system of the present application;

[0030] Figure 4 is an analysis diagram of the field curvature distortion of the objective lens system of the present application;

[0031] Figure 5 is a structural schematic diagram of an embodiment of the optical system of the present application. DETAILED DESCRIPTION

[0032] In order for those skilled in the art to better understand the technical solutions of the present application, the objective lens system and the optical system provided by the present application are described in further detail below in combination with the drawings and specific embodiments. It can be understood that the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.

[0033] The terms "first", "second", and the like in the present application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device.

[0034] The present application provides an objective lens system, so that the micro-light night vision instrument using the objective lens system has a larger field of view and has a higher resolution in the full field of view. Please refer to Figure 1 , Figure 1 is a structural schematic diagram of an embodiment of the objective lens system of the present application. As shown in Figure 1 , the objective lens system 10 includes a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15 and a sixth lens 16 arranged in sequence along the optical axis direction of the objective lens system 10 from the object side to the image side.

[0035] Specifically, the incident light rays are incident into the objective lens system 10, and are sequentially transmitted through the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15 and the sixth lens 16 to be emitted to the image intensifier protective window 20, so as to realize the magnification and collimation processing of the light rays.

[0036] The first lens 11 has positive focal power, specifically, the first lens 11 is a meniscus lens, and the image side of the first lens 11 is concave. The second lens 12 has negative focal power, specifically, the second lens 12 is a plano-concave lens, and the image side of the second lens 12 is concave. The third lens 13 has positive focal power, specifically, the third lens 13 is a double convex lens. The fourth lens 14 has positive focal power, specifically, the fourth lens 14 is a meniscus lens. The fifth lens 15 has negative focal power, specifically, the fifth lens 15 is a double concave lens. The sixth lens 16 has negative focal power, specifically, the sixth lens 16 is a meniscus lens, and the object side of the sixth lens 16 is concave.

[0037] Specifically, the focal power characterizes the refractive power of the optical system to the incident parallel light beam, the greater the value of the focal power, the more the parallel light beam is folded; when the focal power is greater than 0, that is, the lens with positive focal power produces converging refraction; when the focal power is less than 0, that is, the lens with negative focal power produces diverging refraction.

[0038] Further, the first lens 11 and the sixth lens 16 of the present application are aspherical lenses, and the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 can be spherical lenses or aspherical lenses.

[0039] Alternatively, in other embodiments, the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15 and the sixth lens 16 can all be aspherical lenses; or, the second lens 12 can be a spherical lens, and the first lens 11, the third lens 13, the fourth lens 14, the fifth lens 15 and the sixth lens 16 can all be aspherical lenses; or, the first lens 11 and the sixth lens 16 are aspherical lenses, and the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 can be spherical lenses, etc. Among them, the number of spherical lenses in the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 can be one or more, and the number of aspherical lenses in the second lens 12, the third lens 13, the fourth lens 14 and the fifth lens 15 can be one or more.

[0040] Specifically, by using an aspherical lens as the first lens 11 closest to the object side, the present application adjusts the incident light of the input objective lens system 10 to achieve high-efficiency correction of chromatic aberration of the objective lens system 10, while reducing the size of the lens formed by the objective lens system 10.

[0041] At the same time, by using an aspherical lens as the sixth lens 16 closest to the image side, the present application adjusts the incident light of the output objective lens system 10 to achieve high-efficiency correction of field curvature and distortion of the objective lens system 10, and improve the imaging quality of the objective lens system 10.

[0042] Further, the second lens 12 and the third lens 13 form a first doublet lens, and the fourth lens 14 and the fifth lens 15 form a second doublet lens, so as to correct chromatic aberration and secondary spectrum chromatic aberration of the objective lens system 10.

[0043] Specifically, the objective lens system 10 satisfies the following relationship:

[0044] 1.8 < N < 2.2 d3 <1.95;

[0045] 30 < V < 50 d3 <50;

[0046] wherein, N d3 is the refractive index of the third lens 13, and V d3 is the Abbe number of the third lens 13.

[0047] The third lens 13 satisfying the above relationship is used in the embodiment, so as to balance the correction of chromatic aberration and spherical aberration of the objective lens system 10.

[0048] Different from the objective lens system used in the prior art micro-light night vision mirror, which is mostly a 6-10 piece double Gauss type objective lens structure, the objective lens system 10 can correct chromatic aberration, spherical aberration, field curvature, distortion, chromatic aberration and secondary spectrum chromatic aberration with high efficiency through six lenses with specific structures, so as to realize high-quality imaging and improve imaging quality.

[0049] Specifically, in the embodiment, the objective lens system 10 satisfies the following relationship:

[0050]

[0051] wherein, f1 is the focal length of the first lens 11, and f is the focal length of the objective lens system 10.

[0052] Further, the objective lens system 10 also satisfies the following relationship:

[0053]

[0054] wherein, f4 is the focal length of the fourth lens 14, and f5 is the focal length of the fifth lens 15.

[0055] Optionally, the application provides an embodiment, in which the curvature radius, central thickness, material and weight of the first lens 11 to the sixth lens 16 of the objective lens system 10 are shown in Table 1.

[0056]

[0057]

[0058] Table 1

[0059] Wherein, S1 is the object side of the first lens 11, S2 is the image side of the first lens 11; S3 is the object side of the second lens 12, S4 is the image side of the second lens 12, and S4 is also the object side of the third lens 13 since the second lens 12 and the third lens 13 form the first doublet lens, S5 is the image side of the third lens 13; S6 is the object side of the fourth lens 14, S7 is the image side of the fourth lens 14, and S7 is also the object side of the fifth lens 15 since the fourth lens 14 and the fifth lens 15 form the second doublet lens, S8 is the image side of the fifth lens 15; S9 is the object side of the sixth lens 16, S10 is the image side of the sixth lens 16; S11 is the incident surface of the image intensifier protective window 20.

[0060] Specifically, since the incident surface of the image intensifier protective window 20 is a plane, the radius of curvature of the image intensifier protective window 20 is infinite.

[0061] The center thickness is the distance between the center points of the two mirror surfaces on the optical axis of the objective lens system 10. As shown in Table 1, the center thickness between S1 and S2 is 2.447 mm, i.e. the center thickness between the object side and the image side of the first lens 11 is 2.447 mm, the center thickness between S2 and S3 is 5.583 mm, i.e. the center thickness between the image side of the first lens 11 and the object side of the second lens 12 is 2.447 mm, and the others are sequentially similar.

[0062] Further, it can be known from Table 1 that the sum of the center thicknesses of all the mirror surfaces is 25.899 mm, i.e. the total length of the objective lens system 10 is 25.899 mm. At the same time, it can be known from Table 1 that the total weight of the optical components of the objective lens system 10 is 15.96 g, which is less than 16 g. Compared with the optical system length of 30 mm-35 mm and the weight of 17 g-30 g of the objective lens system used in the prior art micro-light night vision mirror, the objective lens system 10 effectively reduces the optical system length and the weight.

[0063] Further, the focal length of the objective lens system 10 is 22.58 mm, the aperture F number of the objective lens system 10 is 1.2, and the field of view angle of the objective lens system 10 is greater than 40°, specifically 42.4°, i.e. the objective lens system 10 has a larger field of view angle.

[0064] In combination with Figure 1 , further in combination with Figure 2 , Figure 2 is the optical transfer function curve of the objective lens system of the present application. As Figure 2As shown in the figure, the objective system 10 has high resolution in the full field of view, and even in the 60 lp / mm frequency band, the 0 field of view MTF value is as high as 0.7, and the 1 field of view MTF value is as high as 0.25; it can be seen that the objective system 10 provided in the embodiment can meet higher imaging requirements.

[0065] In combination with Figure 1 , further referring to Figure 3 , Figure 3 is a chromatic aberration analysis diagram of the objective system of the present application. As shown in the figure, Figure 3 the chromatic aberration value of the objective system 10 is between (-0.02 mm) and (0.05 mm), and it can be known that the objective system 10 has good correction effect on the chromatic aberration of the low-light night vision imaging band.

[0066] In combination with Figure 1 , further referring to Figure 4 , Figure 4 is a field curvature distortion analysis diagram of the objective system of the present application. As shown in Figure 4 (a), the field curvature of the objective system 10 is controlled within ±0.05 mm, so as to make the sharpness of the imaging picture consistent. Field curvature is also called "image field curvature". When the lens has field curvature, the intersection of the entire light beam does not coincide with the ideal image point, although a clear image point can be obtained at each specific point, but the entire image plane is a curved surface. T represents the meridional field curvature, and S represents the sagittal field curvature. The field curvature curve shows the distance from the current focal plane or image plane to the paraxial focal plane as a function of the field coordinate, the meridional field curvature data is the distance measured along the Z axis from the currently determined focusing plane to the paraxial focal plane, and is measured in the meridional (YZ) plane. The sagittal field curvature data measures the distance measured in a plane perpendicular to the meridional plane, and the baseline in the schematic diagram is on the optical axis, and the top of the curve represents the maximum field of view (angle or height). No units are set on the vertical axis because the curve is always normalized with the maximum radial field of view.

[0067] As shown in Figure 4 (b), the distortion of the objective system 10 is controlled within 2%. Generally speaking, lens distortion is actually a general term for the perspective distortion inherent in optical lenses, that is, the distortion caused by perspective, which is very unfavorable for the imaging quality of a photo, because the purpose of photography is to reproduce, not to exaggerate, but because it is an inherent property of the lens (convex lens converges light, concave lens diverges light), it cannot be eliminated, only improved. As shown in Figure 4 (b), it can be seen that the lens distortion provided in the embodiment is only 2%, which can effectively reduce the distortion of the imaging, so that the human eye cannot perceive the deformation of the picture.

[0068] In conclusion, the power distribution of the six lenses of the objective system 10 with specific structures and specific parameters is reasonable, which realizes efficient correction of the chromatic spherical aberration, field curvature, distortion, chromatic aberration and secondary spectral chromatic aberration of the objective system 10, and further realizes high-quality imaging, improves the imaging quality, and the shapes of the six lenses are convenient for processing.

[0069] Secondly, the focal length of the objective system 10 is 22.58mm, the total length of the objective system 10 is 25.899mm, and the total weight of the optical components of the objective system 10 is less than 16g, which effectively reduces the weight of the objective system 10 and reduces the size of the objective system 10.

[0070] Thirdly, the aperture F number of the objective system 10 is 1.2, that is, the lens aperture is large, which can receive more incident light, which is beneficial to obtain incident light in a low-illumination environment. At the same time, the field of view angle of the objective system 10 is greater than 40°, the 0 field of view MTF value at the frequency of 60lp / mm is as high as 0.7, and the 1 field of view MTF value is as high as 0.25, which can meet the demand of high-resolution imaging, and can be widely applied in night vision devices using image intensifiers.

[0071] The application also provides an optical system, please further refer to Figure 5 , Figure 5 is a structural schematic diagram of an embodiment of the application. As Figure 5 shown, the optical system 50 includes an objective system 51, an image intensifier 52 and an ocular 53. Among them, the objective system 51 is the objective system 10 described in the above embodiment, which will not be repeated here.

[0072] Among them, the objective system 51, the image intensifier 52 and the ocular 53 are sequentially arranged along the optical axis direction of the optical system 50, the objective system 51 is used for acquiring light generated by the target to be imaged, the light is processed by the image intensifier 52 for amplification, and the image of the target to be imaged is formed on the image plane of the ocular 53.

[0073] The above is only an embodiment of the application, and does not limit the patent scope of the application, and any equivalent structure or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the application.

Claims

1. An objective lens system characterized by comprising: The objective lens system is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens arranged in sequence from the object side to the image side along the optical axis direction of the objective lens system, the second lens and the third lens form a first doublet lens, and the fourth lens and the fifth lens form a second doublet lens; The first lens has positive refractive power, the second lens has negative refractive power, the third lens has positive refractive power, the fourth lens has positive refractive power, the fifth lens has negative refractive power, and the sixth lens has negative refractive power; The object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface; The object side surface of the second lens is a convex surface, and the image side surface of the second lens is a concave surface; The image side surface of the third lens is a convex surface; The object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; The image side surface of the fifth lens is a concave surface; The object side surface of the sixth lens is a concave surface, and the image side surface of the sixth lens is a convex surface; The objective lens system satisfies the following relationship: ； wherein is the focal length of the first lens; is the focal length of the objective system.

2. The objective system according to claim 1, characterized in that The first lens and the sixth lens are aspherical lenses.

3. The objective system of claim 1, wherein The total length of the objective lens system is 25.899 mm.

4. The objective system of claim 1, wherein The focal length of the objective lens system is 22.58 mm.

5. The objective system of claim 1, wherein The aperture F number of the objective lens system is 1.

2.

6. The objective system of claim 1, wherein The objective lens system satisfies the following relationship: ； wherein, is the focal length of the fourth lens; is the focal length of the fifth lens.

7. The objective system of claim 1, wherein The objective lens system satisfies the following relationship: 1.8< <1.95； wherein n3is the refractive index of the third lens.

8. The objective system according to claim 7, characterized in that The objective lens system satisfies the following relationship: ； wherein Vd is the Abbe number of the third lens.

9. An optical system characterized by comprising: The optical system comprises the objective lens system according to any one of claims 1-8, an image intensifier and an ocular, the objective lens system is used to obtain light generated by a target to be imaged, the light is processed by the image intensifier for magnification, and an image of the target to be imaged is formed on the image plane of the ocular.

Images