A dual-band catadioptric long focal length four-gear zoom optical system

Abstract

The application discloses a double-waveband folded reflection long-focus four-grade zoom optical system, which comprises, from the object side to the image side, a primary imaging group, a front fixed lens group, a variable magnification lens group, a compensation lens group and a rear fixed lens group, and the optical power distribution is positive, positive, positive, negative and positive in sequence, wherein the primary imaging group is a Cassegrain reflector group composed of a primary mirror and a secondary mirror, the front fixed lens group is composed of four single lenses and one cemented lens, the variable magnification lens group is composed of two double-cemented lenses and one single lens, the compensation lens group is composed of one double-cemented lens with a concave surface facing the image side, and the rear fixed lens group is composed of one negative lens and one positive lens; the Cassegrain reflector group is fused with the zoom lens group, the four-grade zoom function of the long-focus system is realized, and the space volume and weight occupied by the system are greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of space optical system technology, and in particular relates to a dual-band catadioptric zoom optical system. Background Technology

[0002] In the field of airborne optoelectronic imaging systems, television imaging optical systems are responsible for ground reconnaissance and search functions, and are an important component of airborne payloads. To achieve target search and tracking, optical systems need to be capable of both wide field-of-view short focal length and narrow field-of-view long focal length configurations. For tactical and strategic reconnaissance at medium and high altitudes, the focal length of optical systems is typically between 1000 and 3000 mm. Simultaneously, airborne pods should be small in size, lightweight, shock-resistant, and resistant to high and low temperatures. In adverse weather conditions such as fog, dust, and rain, light transmittance is significantly reduced, resulting in insufficient light energy reaching the detector and severely impacting image acquisition. All of these factors place higher demands on optical payloads.

[0003] For long focal length systems with focal lengths in the meter range, a Cassegrain structure is generally used. In airborne environments, a combination of a short focal length zoom system composed of lenses and a long focal length fixed focal length system composed of mirrors is typically used to achieve long focal length zoom functionality. However, this will occupy more pod space and increase weight load. Summary of the Invention

[0004] In view of this, the present invention provides a dual-band catadioptric telephoto four-stop zoom optical system, which can realize the zoom function of the telephoto system, greatly reducing the space and weight occupied. At the same time, the system's band range covers visible light to near-infrared shortwave, enabling image information acquisition in harsh weather environments.

[0005] The technical solution adopted by this invention to solve its technical problem is: a dual-band catadioptric long focal length four-stop zoom optical system, consisting of a primary imaging group, a front fixed lens group, a zoom lens group, a compensation lens group, and a rear fixed lens group, arranged sequentially from the object side to the image side. The optical power distribution of the five lens groups is positive, positive, positive, negative, and positive, respectively. The primary imaging group is a Cassegrain reflector group composed of a primary mirror and a secondary mirror, wherein the primary mirror has a focal length of 200mm or less. f A parabolic mirror with a focal length of 186mm and a diameter of 300mm, and a secondary mirror with a focal length of 1200mm and a diameter of 186mm. fA hyperboloidal mirror with a diameter of 42mm and a focal length of 2 < -100mm is used, with the aperture stop positioned on the secondary mirror. The front fixed lens group, located behind the primary image point, consists of four single lenses and one cemented lens: the first lens is a meniscus negative focal length single lens with its convex surface facing the image plane; the second lens is a meniscus positive focal length single lens with its convex surface facing the image plane; the third lens is a meniscus positive focal length single lens with its convex surface facing the image plane; the fourth lens is a biconcave negative focal length single lens; and the fifth lens is a cemented doublet with its convex surface facing the object plane. The zoom lens group consists of two cemented doublet lenses and one single lens: the first lens is a cemented doublet with its convex surface facing the object plane; the second lens is a biconvex single lens; and the third lens is a cemented doublet with its convex surface facing the object plane. The compensation lens group consists of one cemented doublet with its concave surface facing the image plane. The rear fixed lens group consists of one negative lens and one positive lens: the first lens is a biconcave negative lens, and the second lens is a biconvex positive lens.

[0006] The dual-band catadioptric telephoto four-stop zoom optical system has an interval range of 14.882–111.153 mm between the zoom lens group and the front fixed lens group, an interval range of 3.426–86.151 mm between the compensation lens group and the zoom lens group, and an interval range of 4.461–60.058 mm between the compensation lens group and the rear fixed lens group.

[0007] The aforementioned dual-band catadioptric telephoto four-stop zoom optical system operates in the wavelength ranges of 450nm to 950nm and 900nm to 1700nm, with F-numbers of 3.3, 6.67, 10.6, and 17.8, respectively.

[0008] The aforementioned dual-band catadioptric telephoto four-stop zoom optical system has a front fixed lens group in which the first lens is made of H-ZLAF4LA, the second lens is made of H-ZLAF90, the third lens is made of H-FK95N, the fourth lens is made of H-ZLAF69, and the fifth lens is made of H-FK95N and H-K9L.

[0009] The aforementioned dual-band catadioptric telephoto four-stop zoom optical system has a first lens material of H-FK95N and H-ZBAF52, a second lens material of H-FK95N, and a third lens material of H-BAK4 and H-FK95N in its zoom lens group.

[0010] The aforementioned dual-band catadioptric telephoto four-stop zoom optical system uses H-LAF7 and H-ZPK7 as the materials for its compensation lens group.

[0011] The dual-band catadioptric telephoto four-stop zoom optical system has a first lens made of H-F2 and a second lens made of H-ZLAF68C in the fixed lens group.

[0012] The beneficial effects of this invention are as follows: by integrating the Cassegrain reflector group and the zoom lens group, this invention realizes the four-level zoom function of the long focal length system, which greatly reduces the space volume and weight occupied by the system; by adjusting the glass material of the zoom lens group, the optical system can cover the visible light and near-infrared short waves in the wavelength range, and can achieve stable acquisition of image information in harsh weather environments such as fog, dust, and rain. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the optical system structure of the present invention; Figure 2 This is a schematic diagram of the optical system of the present invention with a focal length of 600mm; Figure 3 This is a schematic diagram of the optical system with a focal length of 1200mm according to the present invention; Figure 4 This is a schematic diagram of the optical system with a focal length of 1900mm according to the present invention; Figure 5 This is a schematic diagram of the optical system with a focal length of 3200mm according to the present invention; Figure 6 This is the MTF diagram of the optical system of the present invention in the visible light band at 600mm; Figure 7 This is the MTF diagram of the optical system of the present invention in the visible light band of 1200mm; Figure 8 This is the MTF diagram of the optical system of the present invention in the visible light band of 1900mm; Figure 9 This is the MTF diagram of the optical system of the present invention in the visible light band of 3200mm; Figure 10 This is the MTF diagram of the optical system in the near-infrared short-wave band of 600mm according to the present invention; Figure 11 The MTF diagram of the optical system in the near-infrared short-wave band of the present invention is shown below. Figure 12 This is the MTF diagram of the optical system in the near-infrared short-wave band of 1900mm of this invention; Figure 13 The MTF diagram of the optical system in the near-infrared short-wave band of the present invention at 3200mm is shown. Figure 14 This is a distortion diagram of the optical system of the present invention in the visible light band at 600mm. Figure 15 This is a distortion diagram of the optical system of the present invention in the visible light band of 1200mm; Figure 16 This is a distortion diagram of the optical system of the present invention in the visible light band at 1900mm. Figure 17This is a distortion diagram of the optical system in the visible light band of 3200mm according to the present invention; Figure 18 This is a distortion diagram of the optical system in the near-infrared short-wave band (600mm) of this invention. Figure 19 This is a distortion diagram of the optical system of the present invention in the near-infrared short-wave band 1200mm. Figure 20 This is a distortion diagram of the optical system of the present invention in the near-infrared short-wave band 1900mm. Figure 21 This is a distortion diagram of the optical system in the near-infrared short-wave band 3200mm of the present invention; Figure 22 This is a dot diagram of the optical system of the present invention in the visible light band of 600mm; Figure 23 This is a dot diagram of the optical system of the present invention in the 1200mm visible light band; Figure 24 This is a dot diagram of the optical system of the present invention in the visible light band of 1900mm; Figure 25 This is a dot diagram of the optical system of the present invention in the visible light band of 3200mm; Figure 26 This is a dot diagram of the optical system of the near-infrared shortwave band 600mm of the present invention; Figure 27 This is a dot diagram of the optical system of the near-infrared shortwave band 1200mm of the present invention; Figure 28 This is a dot diagram of the optical system of the near-infrared shortwave band 1900mm of the present invention; Figure 29 This is a distortion diagram of the optical system in the near-infrared short-wave band 3200mm of the present invention.

[0014] The accompanying figures are labeled as follows: 1—Single imaging group, A—Front fixed lens group, B—Zoom lens group, C—Compensation lens group, D—Rear fixed lens group. Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] like Figure 1As shown in the figure, an embodiment of the present invention provides a dual-band catadioptric telephoto four-stop zoom optical system. From the object side to the image side, the system consists of a primary imaging group 1, a front fixed lens group A, a zoom lens group B, a compensation lens group C, and a rear fixed lens group D. The optical power distribution of the five lens groups is positive, positive, positive, negative, and positive, respectively. The four-stop zoom function is achieved by axially moving the zoom lens group B and the compensation lens group C. The four focal lengths are 600mm, 1200mm, 1900mm, and 3200mm, respectively, with an optical length of less than 385mm. The optical system operates in the wavelength ranges of 450nm to 950nm and 900nm to 1700nm, and the F-numbers range from 3.3 to 6.67 to 10.6 to 17.8, corresponding to the four zoom positions.

[0017] In this embodiment of the invention, Chengdu Guangming Glass was used, which can be applied to a 1920×1080 pixel detector with a pixel size of 4.5μm.

[0018] The optical system is suitable for temperatures ranging from -40℃ to +60℃.

[0019] In an embodiment of the present invention, Figure 2 , Figure 3 , Figure 4 , Figure 5 These are schematic diagrams of the optical system of the four-range zoom optical system described in this invention at the short focal length, medium focal length, medium telephoto, and telephoto positions.

[0020] Specifically, the primary imaging group 1 is a Cassegrain mirror group. The primary mirror is a parabolic mirror with a diameter of 186mm, and the secondary mirror is a hyperboloid mirror with a diameter of 42mm.

[0021] Primary lens focal length 200mm < f 1 < 300mm, secondary lens focal length 1200mm < f 2 < -100mm, the aperture stop is set on the secondary mirror.

[0022] In this embodiment of the invention, the front fixed lens group A is located behind the primary image point and consists of four single lenses and one cemented lens. The first lens is a meniscus negative focal length single lens with its convex surface facing the image plane, made of H-ZLAF4LA; the second lens is a meniscus positive focal length single lens with its convex surface facing the image plane, made of H-ZLAF90; the third lens is a meniscus positive focal length single lens with its convex surface facing the image plane, made of H-FK95N; the fourth lens is a biconcave negative focal length single lens, made of H-ZLAF69; and the fifth lens is a cemented doublet with its convex surface facing the object plane, made of H-FK95N and H-K9L. The position of the front fixed lens group A remains unchanged throughout the zoom process.

[0023] In this embodiment of the invention, the zoom lens group B consists of two cemented doublet lenses and one single lens. The first lens is a cemented doublet with its convex surface facing the object plane, and the materials are H-FK95N and H-ZBAF52; the second lens is a biconvex single lens, and the material is H-FK95N; the third lens is a cemented doublet with its convex surface facing the object plane, and the materials are H-BAK4 and H-FK95N.

[0024] The entire zoom lens group B moves axially between the front fixed lens group A and the compensation lens group C to change the focal length of the entire system; when the system changes from short focal length to long focal length, the zoom lens group B moves in one direction to the front fixed lens group A, and the interval between the zoom lens group B and the front fixed lens group A is 14.882 to 111.153 mm.

[0025] In this embodiment of the invention, the compensation lens group C consists of a cemented doublet lens with its concave surface facing the image plane, and the materials are H-LAF7 and H-ZPK7.

[0026] When the system changes from short focal length to long focal length, the compensation lens group C first moves forward to fix the lens group A and then moves back to fix the lens group D.

[0027] The interval between the compensation lens group C and the zoom lens group B ranges from 3.426 to 86.151 mm.

[0028] In this embodiment of the invention, the rear fixed lens group D consists of a negative lens and a positive lens. The first lens is a biconcave negative lens made of H-F2 material; the second lens is a biconvex positive lens made of H-ZLAF68C material. The spacing between the compensation lens group C and the rear fixed lens group D ranges from 4.461 to 60.058 mm.

[0029] The optical system of this invention can be adapted to two types of image detectors based on the wavelength range. The visible light band is adapted to a detector with a pixel size of 4.5μm and a pixel count of 1920×1080; the near-infrared shortwave band is adapted to a detector with a pixel size of 15μm and a pixel count of 640×480.

[0030] The zoom mechanism of this invention adopts a lead screw structure to achieve rapid zooming. By adjusting the glass material of the zoom lens group, the optical system can cover the visible light and near-infrared short waves, and can achieve stable acquisition of image information in harsh weather environments such as fog, dust, and rain.

[0031] The MTF diagrams of the optical system of this invention at visible light wavelengths of 600mm, 1200mm, 1900mm, and 3200mm are shown below. Figures 6-9 As shown.

[0032] The MTF diagrams of the optical system of this invention in the near-infrared shortwave bands of 600mm, 1200mm, 1900mm, and 3200mm are shown below. Figures 10-13 As shown.

[0033] The optical system distortion diagrams of this invention at visible light wavelengths of 600mm, 1200mm, 1900mm, and 3200mm are shown below. Figures 14-17 As shown.

[0034] The optical system distortion diagrams of this invention in the near-infrared shortwave bands of 600mm, 1200mm, 1900mm, and 3200mm are shown below. Figures 18-21 As shown.

[0035] The point diagrams of the optical system of this invention in the visible light bands of 600mm, 1200mm, 1900mm, and 3200mm are shown below. Figures 22-25 As shown.

[0036] The point diagram of the optical system of this invention in the near-infrared shortwave bands of 600mm, 1200mm, 1900mm and 3200mm is shown below. Figures 26-29 As shown.

[0037] In this embodiment of the invention, the physical parameters of each lens meet the data requirements shown in the table below (Lens Physical Parameter Requirements).

[0038] .

[0039] In this embodiment of the invention, T1, T2, and T3 in the table above represent the air gaps between each group during the zoom process. Specific parameters are shown in the table below (zoom distance size intervals): .

[0040] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A dual-band catadioptric telephoto four-stop zoom optical system, characterized in that: It consists of a primary imaging group (1), a front fixed lens group (A), a zoom lens group (B), a compensation lens group (C), and a rear fixed lens group (D) arranged sequentially from the object side to the image side. The optical power is distributed as positive, positive, positive, negative, and positive in sequence. The working wavelength of the optical system is 450nm~950nm and 900nm~1700nm. The F-numbers of the optical system are 3.3, 6.67, 10.6, and 17.

8. The primary imaging group (1) is a Cassegrain reflector group consisting of a primary mirror and a secondary mirror, wherein the primary mirror has a focal length of 200mm or less. f A parabolic mirror with a focal length of 186mm and a diameter of 300mm, and a secondary mirror with a focal length of 1200mm and a diameter of 186mm. f A hyperboloidal mirror with a diameter of 42mm and a diameter of 2 < -100mm, with the aperture stop set on the secondary mirror; The aforementioned front fixed lens group (A) is located behind the primary image point and consists of four single lenses and one cemented lens: the first lens is a meniscus negative focal length single lens with its convex surface facing the image plane, the second lens is a meniscus positive focal length single lens with its convex surface facing the image plane, the third lens is a meniscus positive focal length single lens with its convex surface facing the image plane, the fourth lens is a biconcave negative focal length single lens, and the fifth lens is a cemented doublet, the first of which is a biconvex lens and the second lens is a meniscus lens with its convex surface facing the image side. The zoom lens group (B) consists of two cemented doublet lenses and one single lens: the first lens is a cemented doublet lens, the first lens of which is a biconvex lens and the second lens is a meniscus lens with its convex surface facing the image side; the second lens is a biconvex single lens; and the third lens is a cemented doublet lens, the first lens of which is a biconvex lens and the second lens is a meniscus lens with its convex surface facing the image side. The compensation lens group (C) consists of cemented doublet lenses, the second lens of which is a biconcave lens and the first lens is a meniscus lens with its convex surface facing the image side. The rear fixed lens group (D) consists of a negative lens and a positive lens: the first lens is a biconcave negative lens, and the second lens is a biconvex positive lens.

2. The dual-band catadioptric telephoto four-stop zoom optical system according to claim 1, characterized in that, The interval between the zoom lens group (B) and the front fixed lens group (A) is 14.882 to 111.153 mm, the interval between the compensation lens group (C) and the zoom lens group (B) is 3.426 to 86.151 mm, and the interval between the compensation lens group (C) and the rear fixed lens group (D) is 4.461 to 60.058 mm.

3. The dual-band catadioptric telephoto four-stop zoom optical system according to claim 2, characterized in that, The first lens in the front fixed lens group (A) is made of H-ZLAF4LA, the second lens is made of H-ZLAF90, the third lens is made of H-FK95N, the fourth lens is made of H-ZLAF69, and the fifth lens is made of H-FK95N and H-K9L.

4. The dual-band catadioptric telephoto four-stop zoom optical system according to claim 2, characterized in that, The first lens in the zoom lens group (B) is made of H-FK95N and H-ZBAF52, the second lens is made of H-FK95N, and the third lens is made of H-BAK4 and H-FK95N.

5. The dual-band catadioptric telephoto four-stop zoom optical system according to claim 2, characterized in that, The compensating lens group (C) is made of H-LAF7 and H-ZPK7 materials.

6. The dual-band catadioptric telephoto four-stop zoom optical system according to claim 2, characterized in that, The first lens in the rear fixed lens group (D) is made of H-F2 material, and the second lens is made of H-ZLAF68C material.

Images