Large aperture refractive telescope objective

Abstract

The application discloses a large-aperture refractive telescope objective, which comprises eight lenses arranged in sequence along an optical axis from an object side to an image side, and air gaps between a first lens and a second lens and between a sixth lens and a seventh lens divide the whole telescope objective into three parts, the first lens constitutes a first part alone and is used for reducing the aperture of a rear-end lens and collecting large-view-angle light into the rear-end lens, the second lens to the sixth lens constitute a second part and are used for correcting aberration of the telescope objective, and the seventh lens and the eighth lens constitute a third part and are used for bearing optical power of the system. The telescope objective system has high robustness, compact structure, small assembling and adjusting difficulty, proper back aperture, and is favorable for installation of a detector, and has equal working F number and image F number, high relative luminance, large aperture and large view field, and the lens can adapt to long-term work in various environments.

Description

Technical Field

[0001] This invention belongs to the field of optics, specifically relating to a large-aperture refractive telescope objective. Background Technology

[0002] Telescopes have a history of over 400 years. The development of astronomy has placed higher demands on astronomical observation equipment. To achieve higher spatial resolution and observation efficiency, large-aperture, wide-field-of-view space telescopes have emerged to meet the needs of observing distant, faint objects. The article "Structural Design and Thermal Control Research of Ground-Based Large-Aperture Telescopes" states that the aperture of a telescope roughly doubles every 40 years. Currently, telescopes with apertures of 1 meter and above are mainly reflecting and catadioptric, with relatively few fully refracting meter-class telescopes. Furthermore, a long-standing problem in astronomy is the inability to simultaneously achieve a large aperture and a wide field of view. However, refracting telescope objectives offer advantages over reflecting telescopes, such as unobstructed views and a large field of view. Specifically, in 2021, *Frontier Information* reported the launch of the Tibet Planetarium's project to construct a one-meter-class optical astronomical telescope with dual functions of scientific research and popular science. This project will be the world's largest aperture refracting optical telescope. Summary of the Invention

[0003] The purpose of this invention is to provide a large-aperture refractive telescope objective lens, which has the advantages of large aperture, large field of view, high relative illumination, compact structure, reasonable back intercept, and high robustness.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A large-aperture refractive telescope objective includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially along the optical axis from the object side to the image side. The air gaps between the first and second lenses, and between the sixth and seventh lenses, divide the entire telescope objective into three parts. The first lens alone constitutes the first part, used to reduce the aperture of the rear lens and collect large field-of-view light rays into the rear lens. The second to sixth lenses form the second part, used to correct aberrations of the objective, satisfying d12 / TTL>=0.3 and d67 / TTL>=0.15, where d12 is the distance between the first and second lenses, d67 is the distance between the sixth and seventh lenses, and TTL is the total optical length. The seventh and eighth lenses form the third part, used to handle the system's optical power, satisfying... in, The optical power of the first part; The optical power is for the second part; This represents the optical power of the third part; all three parts have positive optical power values.

[0006] Furthermore, the eight lenses are: a positive lens with a convex-concave surface, a negative lens with a convex-concave or concave-concave surface, a positive lens with a convex-convex surface, a positive lens with a convex-concave surface, a negative lens with a concave-concave surface, a positive lens with a convex-concave surface, a positive lens with a convex-convex surface, and a negative lens with a convex-concave surface.

[0007] Furthermore, the aperture stop is located on the front surface of the first lens, or in front of the first lens, so that the working F-number and the image-side F-number are equal, and the entire telescope objective lens has no other light-blocking elements except for the aperture stop.

[0008] Furthermore, the telescope objective lens satisfies TTL / D <= 2.8; BFL / TTL >= 0.025; FOV / (f / D) >= 3.24, and F-number = f / D < 1.3; where D is the entrance pupil diameter, BFL is the back intercept, FOV is the field of view, and f is the focal length.

[0009] Furthermore, the focal length f of the telescope objective is 1200-1300mm; the entrance pupil diameter D is 1050-1200mm; the field of view (FOV) is 3.5-4°; the wavelength is 500-800nm; the total optical length (TTL) is 2900-3240mm; and the star size (RMS RADIUS) is ≤10μm.

[0010] Furthermore, the telescope objective lens adopts a fully refractive structure.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] 1. This invention adopts a "positive-positive-positive" optical architecture. Gradually bending the light beam results in a smooth overall light trend, leading to high system robustness. The reasonable spacing between the lenses minimizes installation and adjustment difficulty. It satisfies TTL / D <= 2.8, resulting in a compact structure. It also satisfies BFL / TTL >= 0.025, providing a suitable backstop, which is beneficial for detector installation. Among these: The optical power of the first part, which is solely composed of lens 1; The optical power of the second part of the optical system is the lens group consisting of lenses 2-6. The optical power is the third part of the optical system, consisting of lens group 7-8.

[0013] 2. In this invention, the aperture stop is located on the first surface of the first lens or in front of the first lens, avoiding distortion caused by lenses in front of the aperture stop, thus ensuring that the working F-number and the image-side F-number are equal (WFNO = FNO). Simultaneously, the entire system, except for the aperture stop, has no other light-blocking components, resulting in high relative illumination. Changing the aperture stop position can increase the working F-number to improve image quality, but this does not depart from the essential characteristics of this invention.

[0014] 3. The present invention satisfies FOV / (f / D)>=3.24 and F number=f / D<1.3, and has the advantages of large relative aperture and large field of view.

[0015] 4. This invention adopts a fully refractive structure, which enables the lens to adapt to various environments and work for a long time with low maintenance costs.

[0016] 5. The embodiments provided by this invention are pure spherical structures, which can effectively reduce processing costs. To improve image quality, one or more imaging surfaces can be changed to aspherical surfaces, which does not depart from the essential characteristics of this invention. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the optical system in Example 1.

[0018] Figure 2 This is a structural diagram of the optical system in Example 2.

[0019] The markings in the diagram are: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Eighth lens; 9. Aperture stop. Detailed Implementation

[0020] To make the objectives and technical solutions of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and embodiments. The drawings are for illustrative purposes only and are not strictly drawn to scale; that is, the shape of the spherical or aspherical surface is not limited to the shapes of the spherical or aspherical surfaces shown in the drawings.

[0021] Unless otherwise specified, all terms used in this specification (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so defined herein.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. For example, although the aperture 9 in Embodiment 1 is on the front surface of the first lens 1, it can also be placed in front of the first lens 1, as in Embodiment 2. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] An exemplary embodiment of this application provides a refractive telescope objective lens, which may include a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, and an eighth lens 8 arranged sequentially along the optical axis from the object side to the image side. The first lens is a positive meniscus lens, the second lens is a negative power lens, the third lens is a positive biconvex lens, the fourth lens is a positive meniscus lens, the fifth lens is a negative biconcave lens, the sixth lens is a positive meniscus lens, the seventh lens is a positive biconvex lens, and the eighth lens is a negative meniscus lens.

[0024] The refractive telescope objective of this application, through the rational configuration of the optical power and surface shape of each lens, achieves clear imaging of distant, faint objects within the visible light range. The large air gaps between the first and second lenses, and between the sixth and seventh lenses, divide the entire telescope objective into three parts, each serving to achieve a large field of view, aberration reduction, and a large relative aperture, respectively. By giving the first lens positive optical power, the aperture of the rear lenses can be reduced. Furthermore, making the first lens a meniscus lens with a convex-concave surface allows for the collection of as much light as possible from a large field of view into the rear lenses, increasing the light transmission of the optical lens and helping to fix the direction of large-angle light rays at the edges, thus contributing to a large field of view. By giving the second lens negative optical power and making its image-side surface concave, light rays can be slightly diverged, adjusting the refraction angle and reducing axial chromatic aberration of the optical lens. By giving the third lens positive optical power and a biconvex surface, light rays can be converged, facilitating a smoother entry of light into the rear lenses and adjusting aberration coefficients such as spherical aberration in the second lens group. By rationally configuring the optical power and surface shape of the fourth lens, the direction of light refraction is reduced, thus lowering the system's tolerance sensitivity. By rationally configuring the optical power of the fifth lens, spherical aberration and field curvature are adjusted, achieving clear imaging. Furthermore, the concave object side enhances the lens's relative illumination. By giving the sixth lens positive optical power and making it a meniscus lens, aberrations are further reduced, image quality improved, and distortion optimized. It also allows for effective and smooth light convergence, further reducing the aperture of the rear lens elements. The lens group consisting of the second to sixth lenses primarily provides complementary aberrations to the other lenses, ensuring clear imaging of the entire system. By giving the seventh lens positive optical power and ensuring its object side curvature aligns with the image side curvature of the sixth lens, a smooth light transition is achieved, increasing the system's robustness. The eighth lens, with negative optical power and a meniscus lens, further reduces field curvature and, together with the seventh lens, forms a lens group capable of handling high optical power, thus achieving a large relative aperture.

[0025] Example 1

[0026] This embodiment provides a method such as Figure 1The large-aperture refractive telescope objective lens shown has its first surface, the first surface of the first lens 1, being the surface where the aperture stop 9 is located. The parameters of Embodiment 1 are as follows, and it has a larger aperture than Embodiment 2.

[0027] Focal length (f): 1210mm

[0028] Entrance pupil diameter (D): 1200mm

[0029] Field of view (FOV): 3.5°

[0030] Wavelength: 500-800nm

[0031] Total optical length (TTL): 3236mm

[0032] Star size (RMS RADIUS): ≤10μm

[0033] Back intercept (BFL): 80.5113 mm

[0034] The distance (d12) between the first and second lenses: 1227.1599 mm

[0035] The distance between the sixth and seventh lenses (d67) is 633.9881 mm.

[0036] And it satisfies the following condition:

[0037] F number = f / D = 1.008 < 1.3, large relative caliber.

[0038] FOV / (f / D) >= 3.24, large field of view.

[0039] With d12 / TTL>=0.34 and d67 / TTL>=0.19, the large air gap divides the optical system into three parts.

[0040] A BFL / TTL ratio of 0.025 indicates a suitable backstop, which is beneficial for detector installation.

[0041] TTL / D <= 2.8, compact structure.

[0042] Table 1 Example 1 Optical Power Allocation

[0043]

[0044] in The optical power of the optical system; The optical power of the first portion formed solely by the first lens 1; The optical power of the second part of the optical system is the lens group consisting of the second lens 2 to the sixth lens 6. The optical power of the third part of the optical system is given by the lens group consisting of the seventh lens (7) and the eighth lens (8). The data in Table 1 can be easily obtained... It can be seen that the optical power of the entire optical system is mainly distributed in the third part, which consists of the seventh lens 7 and the eighth lens 8. The optical power of the three parts is positive. The three parts form a "positive positive positive" optical structure, which gradually bends the light rays, making the overall light trend smooth and the system has high robustness.

[0045] Example 1 consists of 8 lenses. The optical power and shape of the 8 lenses along the optical axis from the object side to the image side are as follows: positive, convex-concave; negative, convex-concave; positive, convex-convex; positive, convex-concave; negative, concave-concave; positive, convex-concave; positive, convex-convex; negative, convex-concave. The basic parameters of Example 1 are shown in Table 2, where the units for radius of curvature and thickness are millimeters (mm).

[0046] Table 2 Optical structure parameters of Example 1

[0047]

[0048]

[0049] Example 2

[0050] This embodiment provides a method such as Figure 2 The large-aperture refractive telescope objective shown has an aperture stop 9 located in front of the first lens 1. The parameters of Embodiment 2 are as follows, and it has a larger field of view compared to Embodiment 1.

[0051] Focal length (f): 1300mm

[0052] Entrance pupil diameter (D): 1050mm

[0053] Full field of view (FOV): 4°

[0054] Wavelength: 500-800nm

[0055] Total optical length (TTL): 2940mm

[0056] Star size (RMS RADIUS): ≤10μm

[0057] Back intercept (BFL): 79.6002 mm

[0058] The distance (d12) between the first lens and the second lens: 1022.3107mm

[0059] The distance between the sixth and seventh lenses (d67): 582.2345 mm

[0060] And it satisfies the following condition:

[0061] F number = f / D = 1.238 < 1.3, large relative caliber.

[0062] FOV / (f / D) >= 3.24, large field of view.

[0063] d12 / TTL>=0.34, d67 / TTL>=0.19, large air gap, dividing the optical system into three parts. BFL / TTL>=0.025, suitable backstop, which is beneficial for detector installation.

[0064] TTL / D <= 2.8, compact structure.

[0065] Table 3 Example 2 Optical Power Allocation

[0066]

[0067] in The optical power of the optical system; The optical power of the first portion formed solely by the first lens 1; The optical power of the second part of the optical system is the lens group consisting of the second lens 2 to the sixth lens 6. The optical power of the third part of the optical system is represented by the lens group consisting of the seventh lens (7) and the eighth lens (8). The data in Table 3 can be easily obtained... It can be seen that the optical power of the entire optical system is mainly distributed in the third part, which consists of the seventh lens 7 and the eighth lens 8. The optical power of the three parts is positive. The three parts form a "positive positive positive" optical structure, which gradually bends the light rays, making the overall light trend smooth and the system has high robustness.

[0068] Example 2 consists of 8 lenses. The optical power and shape of the 8 lenses along the optical axis from the object side to the image side are as follows: positive, convex-concave; negative, concave-concave; positive, convex-convex; positive, convex-concave; negative, concave-concave; positive, convex-concave; positive, convex-convex; negative, convex-concave. The basic parameters of Example 2 are shown in Table 4, where the units for radius of curvature and thickness are millimeters (mm).

[0069] Table 4 Optical structure parameters of Example 2

[0070]

[0071]

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, scaling the present invention proportionally to achieve higher angular resolution or to reduce costs should also be within the scope of protection of the present invention.

Claims

1. A large-aperture refractive telescope objective lens, characterized in that, The objective lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens arranged sequentially from the object side to the image side along the optical axis. The eight lenses are respectively: a positive lens with a convex-concave surface, a negative lens with a convex-concave or concave-concave surface, a positive lens with a convex-convex surface, a positive lens with a convex-concave surface, a negative lens with a concave-concave surface, a positive lens with a convex-convex surface, and a negative lens with a convex-concave surface. The air gap between the first and second lenses and the air gap between the sixth and seventh lenses divide the entire telescope objective lens into three parts. The first lens alone constitutes the first part, which is used to reduce the aperture of the rear lens and collect large field-of-view light rays into the rear lens. The second to sixth lenses constitute the second part, which is used to correct the aberrations of the objective lens and satisfy 0.379≥d12 / TTL≥0.

3. 0.198≥d67 / TTL≥0.15, where d12 is the distance between the first and second lenses, d67 is the distance between the sixth and seventh lenses, and TTL is the total optical length. The seventh and eighth lenses form the third part, which is used to handle the optical power of the system, satisfying the condition... ,in, The optical power of the first part; The optical power is for the second part; This represents the optical power of the third part; all three parts have positive optical power values.

2. The large-aperture refractive telescope objective lens according to claim 1, characterized in that, The aperture stop is located on the front surface of the first lens, or in front of the first lens, so that the working F-number and the image-side F-number are equal, and the entire telescope objective lens has no other light-blocking components except for the aperture stop.

3. The large-aperture refractive telescope objective lens according to claim 1, characterized in that, The telescope objective lens satisfies the following conditions: TTL / D <= 2.8; BFL / TTL >= 0.025; FOV / (f / D) >= 3.24; and F-number = f / D < 1.

3. Where D is the entrance pupil diameter, BFL is the back intercept, FOV is the field of view, and f is the focal length.

4. The large-aperture refractive telescope objective lens according to claim 1, characterized in that, The telescope objective has a focal length f of 1200-1300mm; an entrance pupil diameter D of 1050-1200mm; a field of view (FOV) of 3.5-4°; a wavelength of 500-800nm; a total optical length (TTL) of 2900-3240mm; and a star size (RMS RADIUS) ≤ 10μm.

5. The large-aperture refractive telescope objective lens according to claim 1, characterized in that, The telescope objective lens adopts a fully refractive structure.

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