Telescopic optical systems and telescopes

Abstract

The present invention discloses a telescopic optical system, comprising 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 from the object side to the image side; the first lens has positive focal power, the second lens has negative focal power, the third lens has negative focal power, the fourth lens has positive focal power, the fifth lens has positive focal power, the sixth lens has positive focal power, and the seventh lens has negative focal power. By arranging a combination of lenses of different structures, the telescopic optical system rationally distributes the focal power of each lens. While ensuring the magnification of the telescopic optical system, the overall size and weight of the system are reduced, which is conducive to the miniaturization of the finished device and convenient portability. At the same time, it can reduce production costs and facilitate popularization and use.

Description

Technical Field

[0001] The present invention relates to the technical field of optical lenses, and in particular to a telescopic optical system and a telescope. Background Art

[0002] Traditional telescopes are large and heavy, making them unsuitable for extended use. The standard magnification of mainstream telescopes on the market currently ranges from 6x to 12x, a relatively low magnification that is insufficient for viewing small objects at longer distances, such as the stars and birds. Achieving a higher magnification would significantly increase the system's size and weight. Furthermore, to maintain magnification and image quality, existing products on the market use a large number of lenses, some even employing aspherical lenses, which are costly and expensive. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a telescopic optical system with high magnification, small system size and low manufacturing cost.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a telescopic optical system, including 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 from the object side to the image side; the first lens has positive focal power, the second lens has negative focal power, the third lens has negative focal power, the fourth lens has positive focal power, the fifth lens has positive focal power, the sixth lens has positive focal power, and the seventh lens has negative focal power.

[0005] The beneficial effects of the present invention are as follows: the telescopic optical system, by arranging a combination of lenses of different structures and rationally distributing the optical focal length of each lens, reduces the overall size and weight of the system while ensuring the magnification of the telescopic optical system, which is conducive to the miniaturization of the finished device and convenient portability, and at the same time can reduce the production cost and facilitate its popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 Schematic diagram of the structure of the telescopic optical system according to the first embodiment of the present invention;

[0007] Figure 2 Schematic diagram of surface numbering of the telescopic optical system according to the first embodiment of the present invention;

[0008] Figure 3 An MTF curve diagram of an ideal lens with a focal length of 5 mm set at the exit pupil position of the telescopic optical system according to the first embodiment of the present invention;

[0009] Figure 4 This is a graph showing how the MTF value of the telescopic optical system according to the first embodiment of the present invention changes with the field of view at a specific spatial frequency;

[0010] Figure 5 This is the dispersion pattern of the telescopic optical system in the afocal mode according to the first embodiment of the present invention.

[0011] Description of labels:

[0012] 1. First lens;

[0013] 2. Second lens;

[0014] 3. The third lens;

[0015] 4. The fourth lens;

[0016] 5. Fifth lens;

[0017] 6. Sixth lens;

[0018] 7. Seventh lens;

[0019] 8. Aperture;

[0020] 9. Dove prism;

[0021] 10. Right-angle prism;

[0022] 11. Neutral density filter. DETAILED DESCRIPTION

[0023] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0024] Please refer to Figures 1 to 5 , a telephoto optical system, comprising a first lens 1, a second lens 2, an aperture 8, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a seventh lens 7, which are arranged in sequence from the object side to the image side; the first lens 1 has positive focal power, the second lens 2 has negative focal power, the third lens 3 has negative focal power, the fourth lens 4 has positive focal power, the fifth lens 5 has positive focal power, the sixth lens 6 has positive focal power, and the seventh lens 7 has negative focal power.

[0025] The beneficial effects of the present invention are as follows: the telescopic optical system, by arranging a combination of lenses of different structures and rationally distributing the optical focal length of each lens, reduces the overall size and weight of the system while ensuring the magnification of the telescopic optical system, which is conducive to the miniaturization of the finished device and convenient portability, and at the same time can reduce the production cost and facilitate its popularization and use.

[0026] Furthermore, the object-side surface and the image-side surface of the first lens 1 are both convex surfaces; the object-side surface of the second lens 2 is concave, and the image-side surface of the second lens 2 is a plane; the object-side surface of the third lens 3 is a plane, and the image-side surface of the third lens 3 is a concave surface; the object-side surface and the image-side surface of the fourth lens 4 are both convex surfaces; the object-side surface of the fifth lens 5 is convex, and the image-side surface of the fifth lens 5 is concave; the object-side surface and the image-side surface of the sixth lens 6 are both convex surfaces; and the object-side surface and the image-side surface of the seventh lens 7 are both concave surfaces.

[0027] Furthermore, a dove prism 9 is provided between the second lens 2 and the aperture 8, and a right-angle prism 10 is provided between the aperture 8 and the third lens 3; the second lens 2, the dove prism 9, the aperture 8, the right-angle prism 10 and the third lens 3 satisfy: 0.6 28 / TL<0.8,0.03 83 / TL<0.07, where A 28 is the sum of the air distance between the second lens 2 and the aperture 8 and the equivalent thickness of the Dove prism 9, TL is the overall length of the telescopic optical system, A 83 It is the sum of the air distance between the aperture 8 and the third lens 3 and the equivalent thickness of the right-angle prism 10.

[0028] As can be seen from the above description, Dove prism 9 and right-angle prism 10 can redirect the optical path, facilitating the telescopic optical system's adaptation to the interior space of a finished device or reducing its overall length. Aperture stop 8 is positioned at a suitable ratio between second lens element 2 and third lens element 3 to ensure the telescopic optical system's magnification.

[0029] Furthermore, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 satisfy the following conditions:

[0030] f 1-2 >200;

[0031] 0 <f 3-7 <20;

[0032] 0.5 <f 3-5 / f 3-7 <2;

[0033] -6 <f 6-7 / f 3-7 <-2;

[0034] 1 <TL / f 1-2 <1.5;

[0035] where f 1-2 ​​is the combined focal length of the first lens 1 and the second lens 2, f 3-7 is the combined focal length of the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7, f 3-5 is the combined focal length of the third lens 3, the fourth lens 4 and the fifth lens 5, f 6-7 is the combined focal length of the sixth lens 6 and the seventh lens 7, and TL is the overall length of the telephoto optical system.

[0036] As can be seen from the above description, the system's magnification is maintained by controlling the focal lengths of the objective lens and eyepiece. The first lens 1 and the second lens 2 combine to form the objective lens, which collects object-side light and converges it within the optical system to form an intermediate image. The third lens 3, the fourth lens 4, and the fifth lens 5 combine to form the eyepiece. Their relatively short combined focal length allows for rapid convergence of the intermediate image within a relatively small space, facilitating system size reduction and miniaturization.

[0037] Furthermore, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6 and the seventh lens 7 satisfy:

[0038] |Nd1-Nd2|>0.15;

[0039] Nd3>1.7;

[0040] Nd4>1.7;

[0041] |Nd6-Nd7|>0.2;

[0042] Wherein, Nd1 is the refractive index of the first lens 1 , Nd2 is the refractive index of the second lens 2 , Nd3 is the refractive index of the third lens 3 , Nd4 is the refractive index of the fourth lens 4 , Nd6 is the refractive index of the sixth lens 6 , and Nd7 is the refractive index of the seventh lens 7 .

[0043] As can be seen from the above description, each lens is made of a material with a reasonable refractive index, especially the third lens 3 and the fourth lens 4 are both made of a high refractive index material, so as to converge the light from the intermediate image plane in a smaller space, which is conducive to miniaturization of the system.

[0044] Furthermore, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6 and the seventh lens 7 satisfy:

[0045] |Vd1-Vd2|>20;

[0046] Vd3<50;

[0047] Vd4<50;

[0048] |Vd6-Vd7|>25;

[0049] Wherein, Vd1 is the dispersion coefficient of the first lens 1, Vd2 is the dispersion coefficient of the second lens 2, Vd3 is the dispersion coefficient of the third lens 3, Vd4 is the dispersion coefficient of the fourth lens 4, Vd6 is the dispersion coefficient of the sixth lens 6, and Vd7 is the dispersion coefficient of the seventh lens 7.

[0050] As can be seen from the above description, the selection of materials with reasonable dispersion coefficients for each lens, especially the matching of high and low dispersion coefficients of the first lens 1 and the second lens 2, and the matching of high and low dispersion coefficients of the sixth lens 6 and the seventh lens 7, are beneficial to eliminating system chromatic aberration and ensuring imaging effects at large magnifications.

[0051] Furthermore, a neutral density filter 11 is included, and the neutral density filter 11 is arranged on the object side of the first lens 1 .

[0052] As can be seen from the above description, under strong light conditions, the neutral density filter 11 can attenuate the light entering the optical system to avoid overexposure when viewing the picture.

[0053] Furthermore, the aperture FNO of the telescopic optical system is 12.5.

[0054] From the above description, it can be seen that a sufficiently large aperture can allow sufficient light to enter the system, and a high-definition image can still be obtained at a large magnification.

[0055] The telescope comprises a lens barrel and the above-mentioned telescopic optical system, wherein the telescopic optical system is installed in the lens barrel.

[0056] From the above description, it can be seen that the telescope has a high magnification, a small system size, and a low manufacturing cost.

[0057] Please refer to Figures 1 to 5 , Embodiment 1 of the present invention is: a telescope, comprising a lens barrel and a telescopic optical system, wherein the telescopic optical system is installed in the lens barrel.

[0058] The telescopic optical system includes a first lens 1, a second lens 2, an aperture 8, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6 and a seventh lens 7, which are arranged in sequence from the object side to the image side; the first lens 1 has positive focal power, the second lens 2 has negative focal power, the third lens 3 has negative focal power, the fourth lens 4 has positive focal power, the fifth lens 5 has positive focal power, the sixth lens 6 has positive focal power, and the seventh lens 7 has negative focal power.

[0059] Specifically, the first lens 1 and the second lens 2 are combined to form an objective lens, and the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are combined to form an eyepiece. In this embodiment, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 are all glass spherical lenses. The object side and image side of the first lens 1 are both convex; the object side of the second lens 2 is concave, and the image side of the second lens 2 is flat; the object side of the third lens 3 is flat, and the image side of the third lens 3 is concave; the object side and image side of the fourth lens 4 are both convex; the object side of the fifth lens 5 is convex, and the image side of the fifth lens 5 is concave; the object side and image side of the sixth lens 6 are both convex; and the object side and image side of the seventh lens 7 are both concave. The first lens 1 and the second lens 2 are glued together, and the sixth lens 6 and the seventh lens 7 are glued together.

[0060] A dove prism 9 is further provided between the second lens 2 and the aperture 8, and a right-angle prism 10 is further provided between the aperture 8 and the third lens 3. In this embodiment, both the dove prism 9 and the right-angle prism 10 are made of glass. The first lens 1 and the second lens 2 are coaxially arranged, and the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 are coaxially arranged, with the axial directions of the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 being perpendicular to the circumferential directions of the first lens 1 and the second lens 2. The dove prism 9 and the right-angle prism 10 can change the direction of the optical path, which is beneficial for adapting the present telescopic optical system to the internal space of a finished device or reducing the overall length of the finished device.

[0061] The second lens 2, the dove prism 9, the aperture 8, the right-angle prism 10 and the third lens 3 meet the following requirements: 0.6 28 / TL<0.8,0.03 83 / TL<0.07, where A 28 is the sum of the air distance between the second lens 2 and the aperture 8 and the equivalent thickness of the Dove prism 9, TL is the overall length of the telephoto optical system, A 83 It is the sum of the air distance between the aperture 8 and the third lens 3 and the equivalent thickness of the right-angle prism 10.

[0062] The first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7 meet the following requirements:

[0063] f 1-2 >200;

[0064] 0 <f 3-7 <20;

[0065] 0.5 <f 3-5 / f 3-7 <2; ​​

[0066] -6 <f 6-7 / f 3-7 <-2;

[0067] 1 <TL / f 1-2 <1.5;

[0068] where f 1-2 is the combined focal length of the first lens 1 and the second lens 2, f 3-7 is the combined focal length of the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6 and the seventh lens 7, f 3-5 is the combined focal length of the third lens 3, the fourth lens 4 and the fifth lens 5, f 6-7 is the combined focal length of the sixth lens 6 and the seventh lens 7, and TL is the overall length of the telephoto optical system.

[0069] The first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6 and the seventh lens 7 meet the following requirements:

[0070] |Nd1-Nd2|>0.15;

[0071] Nd3>1.7;

[0072] Nd4>1.7;

[0073] |Nd6-Nd7|>0.2;

[0074] Wherein, Nd1 is the refractive index of the first lens 1 , Nd2 is the refractive index of the second lens 2 , Nd3 is the refractive index of the third lens 3 , Nd4 is the refractive index of the fourth lens 4 , Nd6 is the refractive index of the sixth lens 6 , and Nd7 is the refractive index of the seventh lens 7 .

[0075] The first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the sixth lens 6 and the seventh lens 7 meet the following requirements:

[0076] |Vd1-Vd2|>20;

[0077] Vd3<50;

[0078] Vd4<50;

[0079] |Vd6-Vd7|>25;

[0080] Wherein, Vd1 is the dispersion coefficient of the first lens 1, Vd2 is the dispersion coefficient of the second lens 2, Vd3 is the dispersion coefficient of the third lens 3, Vd4 is the dispersion coefficient of the fourth lens 4, Vd6 is the dispersion coefficient of the sixth lens 6, and Vd7 is the dispersion coefficient of the seventh lens 7.

[0081] The telescopic optical system further includes a neutral density filter 11 , which is disposed on the object side of the first lens 1 .

[0082] In this embodiment, the objective lens focal length of the telescopic optical system, that is, the combined focal length f of the first lens 1 and the second lens 2, is 1-2 =360mm; the focal length of the eyepiece of the telescopic optical system, i.e., the combined focal length f of the third lens 3, the fourth lens 4, the fifth lens 5, the sixth lens 6, and the seventh lens 7 3-7 =15mm; telephoto optical system aperture FNO=12.5; telephoto optical system total length TL=428.7mm, magnification 24X, field of view angle 1.92°.

[0083] The specific parameters of each lens in the telescopic optical system of this embodiment are shown in Table 1 below ( Figure 2 Schematic diagram of surface numbering of the telescopic optical system according to the first embodiment of the present invention):

[0084] Table 1:

[0085]

[0086] Figure 3 、 Figure 4 and Figure 5 is an optical performance chart of the telescopic optical system in this embodiment, wherein Figure 3 The MTF curve of an ideal lens with a focal length of 5mm set at the exit pupil position can be used to evaluate the resolving power of the optical system. As can be seen from the curve in the figure, each MTF curve is close to the diffraction limit, indicating that the various aberrations of the system have been well corrected; Figure 4 This is a curve showing the MTF value variation with field of view at a specific spatial frequency for the telescopic optical system according to Example 1 of the present invention. The MTF values ​​of different fields of view vary very little, indicating that the optical performance of the system is very uniform across the fields of view, with very little difference between the inner and outer fields. Figure 5 This is a dispersion pattern of the telescopic optical system in the afocal mode according to the first embodiment of the present invention. It can be seen from the figure that the dispersion spots of the light rays in each field of view are very small, and the RMS radius is much less than 3 arcmin, further demonstrating that a good imaging effect has been achieved through the telescopic optical system.

[0087] In summary, the telescopic optical system provided by the present invention reduces the overall size and weight of the system while ensuring the magnification of the telescopic optical system by arranging a combination of lenses with different structures and rationally distributing the optical focal length of each lens. This is conducive to the miniaturization of the finished device and makes it easier to carry. At the same time, it can reduce production costs and is conducive to its popularization and use.

[0088] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A telescopic optical system, characterized in that: The optical system comprises a first lens, a second lens, an aperture, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged in sequence from the object side to the image side; the first lens has positive focal power, the second lens has negative focal power, the third lens has negative focal power, the fourth lens has positive focal power, the fifth lens has positive focal power, the sixth lens has positive focal power, and the seventh lens has negative focal power; a dove prism is further provided between the second lens and the aperture, and a right-angle prism is further provided between the aperture and the third lens; The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens satisfy the following requirements: f 1-2 >200； 0<f 3-7 <20； 0.5<f 3-5 / f 3-7 <2; -6<f 6-7 / f 3-7 <-2; 1<TL / f 1-2 <1.5; where f 1-2 is the combined focal length of the first and second lenses, f 3-7 is the combined focal length of the third lens, the fourth lens, the fifth lens, the sixth lens and the seventh lens, f 3-5 is the combined focal length of the third lens, the fourth lens and the fifth lens, f 6-7 is the combined focal length of the sixth lens and the seventh lens, and TL is the overall length of the telephoto optical system.

2. The telescopic optical system according to claim 1, wherein: The object-side surface and the image-side surface of the first lens are both convex surfaces; the object-side surface of the second lens is concave, and the image-side surface of the second lens is a plane; the object-side surface of the third lens is a plane, and the image-side surface of the third lens is a concave surface; the object-side surface and the image-side surface of the fourth lens are both convex surfaces; the object-side surface of the fifth lens is convex, and the image-side surface of the fifth lens is concave; the object-side surface and the image-side surface of the sixth lens are both convex surfaces; and the object-side surface and the image-side surface of the seventh lens are both concave surfaces.

3. The telescopic optical system according to claim 1, wherein: The second lens, dove prism, aperture, right angle prism and third lens meet the following requirements: 0.6 28 / TL<0.8,0.03 83 / TL<0.07, where A 28 is the sum of the air distance between the second lens and the aperture and the equivalent thickness of the Dove prism, TL is the overall length of the telescopic optical system, A 83 It is the sum of the air distance between the aperture and the third lens and the equivalent thickness of the right-angle prism.​​ 4. The telescopic optical system according to claim 1, wherein: The first lens, the second lens, the third lens, the fourth lens, the sixth lens and the seventh lens satisfy the following requirements: |Nd1-Nd2|>0.15; Nd3>1.7; Nd4>1.7; |Nd6-Nd7|>0.2; Wherein, Nd1 is the refractive index of the first lens, Nd2 is the refractive index of the second lens, Nd3 is the refractive index of the third lens, Nd4 is the refractive index of the fourth lens, Nd6 is the refractive index of the sixth lens, and Nd7 is the refractive index of the seventh lens.

5. The telescopic optical system according to claim 1, wherein: The first lens, the second lens, the third lens, the fourth lens, the sixth lens and the seventh lens satisfy the following requirements: |Vd1-Vd2|>20; Vd3<50; Vd4<50; |Vd6-Vd7|>25; Wherein, Vd1 is the chromatic aberration coefficient of the first lens, Vd2 is the chromatic aberration coefficient of the second lens, Vd3 is the chromatic aberration coefficient of the third lens, Vd4 is the chromatic aberration coefficient of the fourth lens, Vd6 is the chromatic aberration coefficient of the sixth lens, and Vd7 is the chromatic aberration coefficient of the seventh lens.

6. The telescopic optical system according to claim 1, wherein: A neutral density filter is also included, and the neutral density filter is arranged on the object side of the first lens.

7. The telescopic optical system according to claim 1, wherein: The aperture FNO of the telephoto optical system is 12.

5.

8. A telescope, characterized in that The telescopic optical system comprises a lens barrel and the telescopic optical system according to any one of claims 1 to 7, wherein the telescopic optical system is installed in the lens barrel.

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