A stereoscopic imaging optical system for a civilian small unmanned aerial vehicle

Abstract

The application is suitable for the field of optical imaging technology, and provides a stereo imaging optical system for civil small unmanned aerial vehicle, which is composed of a spherical positive lens, two groups of double cemented spherical lenses, an aperture, a convex spherical mirror and a concave parabolic mirror, wherein the two groups of double cemented spherical lenses include a first double cemented spherical lens and a second double cemented spherical lens; the application can realize high-resolution imaging at multiple wavelengths, provide rich spectral information for users, and help to more accurately analyze and judge the target area. The compact design makes the system small in size and light in weight, and is very suitable for being mounted on low-altitude civil small unmanned aerial vehicle, thereby expanding the application range and operation ability of the civil unmanned aerial vehicle. The stereo imaging function can obtain three-dimensional information of the target area, and has important application value in the fields of geographic mapping and city planning, and can provide more comprehensive and accurate data compared with the traditional imaging mode.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging technology, and in particular to a stereo imaging optical system for civilian small unmanned aerial vehicles. BACKGROUND

[0002] The existing imaging technology of civilian small unmanned aerial vehicles is limited by the problems of large volume of long focal length and large distortion of wide field of view stereo imaging, and it is difficult to realize high resolution, wide area and small stereo imaging capability. There are the following specific technical deficiencies, covering ground pixel resolution, optical distortion, volume, spectral range of stereo imaging and other key indicators:

[0003] Balancing problem of high ground pixel resolution (GSD) and wide area imaging: The resolution of civilian small unmanned aerial vehicles is mainly related to the focal length of the optical system, the pixel size of the camera sensor and the flight height. Under the premise of certain focal length and pixel size, the ground pixel resolution is inversely proportional to the flight height, so the resolution can be improved by reducing the flight height. For example, taking the DJI Spark 4 multi-spectral version unmanned aerial vehicle as an example, the GSD of the camera of the unmanned aerial vehicle is 9.52 cm / pixel at a height of 180 meters, and the professional surveying and mapping requires GSD≤5 cm / pixel. If 3 cm / pixel is required, the flight height needs to be reduced to about 60 meters. If the observation range is to be kept unchanged, the system's observation field of view must be expanded to 3 times the original, otherwise the work efficiency will be greatly reduced and the flight risk will be increased. Therefore, how to meet the observation range of a large area while ensuring high resolution is a difficulty in the current unmanned aerial vehicle imaging technology.

[0004] Limited distortion control capability of large field of view optical lens: The existing civilian small unmanned aerial vehicles generally use wide-angle lenses to expand the field of view, but the barrel distortion problem is significant. For example, the DJI Spark 4 series has a distortion rate of 5%-8% at the edge of the 4K resolution mode, resulting in a significant curvature of straight lines. Although some models (such as the Spark 4 RTK) reduce distortion through factory single correction, the residual distortion in high resolution mode still needs to rely on post-processing software, increasing the complexity of data processing. In addition, the distortion performance varies greatly under different resolution modes, such as 2.7K and 1080P modes, which usually have a distortion rate of less than 3%, while the 4K mode may double.

[0005] The contradiction between volume and ground pixel resolution is prominent: In the design of civilian unmanned aerial vehicles, the contradiction between ground pixel resolution and the volume of unmanned aerial vehicles is essentially a game between optical physics limitation and engineering constraint. In the design of civilian unmanned aerial vehicles, higher GSD (i.e. finer ground detail capture capability) relies on larger optical systems, while miniaturization requirements require compression of sensor and lens volume. This contradiction runs through the full product design of consumer-grade to professional-grade unmanned aerial vehicles.

[0006] Limitations of the stereo imaging spectral range: the stereo imaging spectral range of traditional civilian small unmanned aerial vehicle cameras is mainly full color, and color imaging is mainly in the Bayer array imaging mode, such as DJI Mavic3 series, and few use multispectral imaging technology for image registration and synthesis; in addition, traditional small stereo multispectral imaging technology relies on external dual lens modules, and the dual modules are applied in a strapdown manner by mechanical fixation, such as Trimble UX5 HP multispectral aerial survey system, which will significantly increase the load weight and volume, and the optical axis calibration is complex, which is difficult to meet the mounting application scenarios of civilian light small unmanned aerial vehicles.

[0007] In summary, the existing technology has many bottlenecks. In terms of volume, the existing large field of view high resolution unmanned aerial vehicle load is generally large in volume due to the requirement of aberration compensation parameters and double linear array, which is difficult to adapt to the application scenarios of light small unmanned aerial vehicles; in terms of functionality, the existing stereo unmanned aerial vehicle load is mainly full color imaging, and few have multispectral stereo imaging capability, which is difficult to meet the detection of ground object spectral information; in terms of performance, the existing unmanned aerial vehicle load, when the resolution reaches 2cm@200m, the optical field of view is generally not large, while the load with large field of view imaging capability has generally low resolution, and the optical distortion is great, which will greatly reduce the three-dimensional reconstruction accuracy. SUMMARY

[0008] In view of the deficiencies of the prior art, the purpose of the present application is to propose a stereo imaging optical system for civilian small unmanned aerial vehicles, which aims to solve the technical problems proposed in the background art.

[0009] A stereo imaging optical system for civilian small unmanned aerial vehicles, the system is composed of a spherical positive lens, two groups of double-cemented spherical lenses, an aperture, a convex spherical mirror and a concave parabolic mirror, the two groups of double-cemented spherical lenses include a first double-cemented spherical lens and a second double-cemented spherical lens.

[0010] The system takes the optical axis as the axis and the direction of light incidence as the arrangement direction, and the order of each optical component is: spherical positive lens, first double-cemented spherical lens, aperture, second double-cemented spherical lens, concave parabolic mirror and convex spherical mirror; the light is incident in the direction of the positive lens to the detector, and passes through the spherical positive lens, the first double-cemented spherical lens, the aperture, the second double-cemented spherical lens, the convex spherical mirror and the concave parabolic mirror in turn, and finally guides the light to the detector for imaging.

[0011] Preferably, the focal length of the optical system is 45.9865mm, the total length of the lens is 50.0021mm, the system aperture value is 5, the half field of view range of the extension rail is 13.5-16.5 degrees, the vertical field of view is 60 degrees, and the working spectrum range includes: full color 0.45-0.72um, multispectral 0.45um, 0.52um, 0.65um, 0.75um.

[0012] Preferably, the spherical positive lens uses material H-ZPK5, and the thickness is 5.502mm.

[0013] Preferably, the first double-cemented spherical lens is made of glass H-FK71 and H-LAF53, and the thicknesses are 3.648mm and 1.761mm respectively; the second double-cemented spherical lens is made of glass H-ZF88 and D-LAF50, and the thicknesses are 1.828mm and 1.352mm respectively; the convex spherical mirror and the concave parabolic mirror have thicknesses of-12.004mm and 17.6599mm respectively, and are used for reflecting light so that the light is finally imaged on the detector.

[0014] Preferably, the air gap between the spherical positive lens and the first double-cemented spherical lens is 8.614mm, the air gap between the first double-cemented spherical lens and the diaphragm is 3.462mm, the air gap between the diaphragm and the second double-cemented spherical lens is 0.168mm, and the air gap between the second double-cemented spherical lens and the mirror group is 18.012mm, and the mirror group is composed of the convex spherical mirror and the concave parabolic mirror.

[0015] The beneficial effects realized by the present application are as follows:

[0016] The present application can realize high-resolution imaging at multiple wavelengths, providing users with rich spectral information, which helps to more accurately analyze and judge the target area. The compact design makes the system small in size and light in weight, which is very suitable for mounting on low-altitude civilian small unmanned aerial vehicles, and expands the application range and operation ability of civilian unmanned aerial vehicles. The stereoscopic imaging function can obtain three-dimensional information of the target area, which has important application value in the fields of geographic mapping and urban planning, and can provide more comprehensive and accurate data compared with traditional imaging methods. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Fig. 1 is a structural schematic diagram of a stereoscopic imaging optical system for a civilian small unmanned aerial vehicle.

[0018] Figure 2 Fig. 2 is an MTF curve of a stereoscopic imaging optical system for a civilian small unmanned aerial vehicle.

[0019] Figure 3This is a distortion curve of a stereo imaging optical system for small civilian drones.

[0020] Figure 4 This is a point diagram of a stereoscopic imaging optical system for small civilian drones.

[0021] Notes on reference numerals: 1 - spherical positive lens, 2 - first double cemented spherical lens, 3 - aperture, 4 - second double cemented spherical lens, 5 - concave parabolic reflector, 6 - convex spherical reflector. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0024] This invention enables high-resolution imaging at multiple wavelengths, providing users with rich spectral information and enabling more accurate analysis and assessment of target areas. The compact design makes the system small and lightweight, making it ideal for mounting on small, low-altitude civilian drones, expanding the application and operational capabilities of civilian drones. The stereoscopic imaging function, which can capture three-dimensional information about target areas, has significant application value in fields such as geographic surveying and urban planning, providing more comprehensive and accurate data than traditional imaging methods.

[0025] The design parameters are as follows:

[0026] 1. Detector parameters: resolution - 16556 pixels (H) × 9200 pixels (V); pixel size 3.2 μm;

[0027] 2. Flight altitude: 200m;

[0028] 3. Ground pixel resolution: better than 2cm;

[0029] 4. Field of view: not less than 60°;

[0030] 5. Distortion: <0.2% in the direction perpendicular to the track;

[0031] 6. Focal length: 45.9865mm;

[0032] 7. F / # : 5.00096;

[0033] Referring to Figure 1 , the embodiment of the present application provides a kind of stereo imaging optical system for small civilian unmanned aerial vehicle, the system is by a piece of spherical positive lens 1, two groups of double cemented spherical lens, a diaphragm 3, a convex spherical mirror 6 and a concave parabolic mirror 5 are formed, two groups of double cemented spherical lens include first double cemented spherical lens 2 and second double cemented spherical lens 4;

[0034] System with optical axis as axis, with light incidence direction as arrangement direction, the order of each optical component is: spherical positive lens 1, first double cemented spherical lens 2, diaphragm 3, second double cemented spherical lens 4, concave parabolic mirror 5 and convex spherical mirror 6;Light is incident to the direction of positive lens to detector, in turn through spherical positive lens 1, first double cemented spherical lens 2, diaphragm 3, second double cemented spherical lens 4, convex spherical mirror 6 and concave parabolic mirror 5, finally guide light to detector imaging.

[0035] In the embodiment, the focal length of the optical system formed is 45.9865mm, the total length of the lens is 50.0021mm, the system aperture value is 5, the range of the half field of view along the track is positive and negative 13.5-16.5 degrees, the vertical track field of view is 60 degrees, and the working spectral range includes: full color 0.45 μm-0.72 μm, multispectral 0.45 μm, 0.52 μm, 0.65 μm, 0.75 μm.

[0036] In the embodiment, spherical positive lens 1 uses material H-ZPK5, which has specific optical properties, and the thickness is 5.502mm, which is calculated according to the initial convergence requirement of light and the overall optical performance of the system.

[0037] In the embodiment, first double cemented spherical lens 2 is made of glass H-FK71 and H-LAF53, with thicknesses of 3.648mm and 1.761mm respectively, and the combination of the two materials effectively corrects aberration;Second double cemented spherical lens 4 is made of glass H-ZF88 and D-LAF50, with thicknesses of 1.828mm and 1.352mm respectively, further optimizing the focusing of light and aberration correction;The thicknesses of convex spherical mirror 6 and concave parabolic mirror 5 are-12.004mm and 17.6599mm respectively, which are used to reflect light, so that light is finally imaged on the detector.

[0038] In this embodiment, the air gap between the spherical positive lens 1 and the first double-cemented spherical lens 2 is 8.614 mm, the air gap between the first double-cemented spherical lens 2 and the diaphragm 3 is 3.462 mm, the air gap between the diaphragm 3 and the second double-cemented spherical lens 4 is 0.168 mm, and the air gap between the second double-cemented spherical lens 4 and the mirror group is 18.012 mm, and the mirror group is composed of a convex spherical mirror 6 and a concave parabolic mirror 5. The precise air gap design ensures the propagation path and interaction of light between each optical element, and realizes precise control of light and imaging optimization.

[0039] Imaging quality:

[0040] (1) MTF: MTF is the most important way to describe the performance of an optical system, which is used to describe the transfer ability of the optical system to different spatial frequencies of target contrast. The weight of the optical system of the present application is biased towards the average MTF of visible light (MTF@156lp / mm>0.2), which can meet the requirements of clear imaging for ground observation, and reference Figure 2 .

[0041] (2) Distortion: Distortion is a kind of geometric aberration in an optical system, which is defined as the nonlinear deformation of the geometric shape of an image, which does not affect the clarity but changes the proportion of the object. The distortion of the optical system of the present application is better than 0.2% in the vertical rail 60º field of view, and reference Figure 3 .

[0042] (3) Point spread function: the point spread function of the optical system refers to Figure 4 , the distribution of different points in the point spread function can be considered as the energy distribution of the diffraction spot, and the imaging quality of the optical system can be judged by the compactness of the energy distribution of the diffraction spot. As can be seen from the figure, the spot size is uniform and round, which can meet the imaging requirements of the high-resolution wide-area multi-spectral stereo imaging optical system for low-altitude perception.

[0043] The multi-spectral stereo image obtained by the present application can clearly see the detailed information of buildings, roads and other information on the ground. In the multi-spectral image, different ground objects show different characteristics at different wavelengths, which is helpful for classification and analysis of land use types. In the aspect of stereo imaging, through the processing of the image, a three-dimensional model of the ground can be constructed, and the height of the building, the slope of the road and other information can be accurately measured.

[0044] It is to be understood that the terminology "including", "comprising", or other derivatives thereof, is intended to be open-ended and also to encompass the inclusion of extra elements or additional steps than those listed, or vice versa. It is also to be understood that the terminology "one or more of", when used in the context of reciting a list of elements or steps, means that at least one, but potentially one or more, of the enumerated elements or steps is / are present, and that the list is not exhaustive of possible elements or steps.

[0045] The preferred embodiments of the present application have been described above with the intent to enable those skilled in the art to make and use it. It will be clear to those skilled in the art that modifications can be made to the preferred embodiments without departing from the spirit and scope of the application, which is defined by the appended claims.

Claims

1. A stereoscopic imaging optical system for a civilian small unmanned aerial vehicle, characterized by, The system is composed of a spherical positive lens (1), two sets of double cemented spherical lenses, a diaphragm (3), a convex spherical mirror (6) and a concave parabolic mirror (5), wherein the two sets of double cemented spherical lenses include a first double cemented spherical lens (2) and a second double cemented spherical lens (4). The system is arranged along the optical axis and the light incidence direction, and the order of the optical components is: the spherical positive lens (1), the first double cemented spherical lens (2), the diaphragm (3), the second double cemented spherical lens (4), the concave parabolic mirror (5) and the convex spherical mirror (6). The light is incident on the detector through the positive lens, and then sequentially passes through the spherical positive lens (1), the first double cemented spherical lens (2), the diaphragm (3), the second double cemented spherical lens (4), the convex spherical mirror (6) and the concave parabolic mirror (5), and finally is guided to the detector for imaging.

2. The stereoscopic imaging optical system for a small civilian unmanned aerial vehicle according to claim 1, characterized in that, The focal length of the optical system is 45.9865 mm, the total length of the lens is 50.0021 mm, the aperture value of the system is 5, the half field of view range along the track is 13.5-16.5 degrees, the field of view range along the vertical track is 60 degrees, and the working spectral range includes: full color 0.45-0.72 μm.

3. The stereoscopic imaging optical system for a small civilian-oriented unmanned aerial vehicle according to claim 1, characterized by, The spherical positive lens (1) is made of material H-ZPK5, and has a thickness of 5.502 mm.

4. The stereoscopic imaging optical system for a small civilian-oriented unmanned aerial vehicle according to claim 3, characterized by, The first double cemented spherical lens (2) is made of glass H-FK71 and H-LAF53, and has thicknesses of 3.648 mm and 1.761 mm, respectively; the second double cemented spherical lens (4) is made of glass H-ZF88 and D-LAF50, and has thicknesses of 1.828 mm and 1.352 mm, respectively; the convex spherical mirror (6) and the concave parabolic mirror (5) have thicknesses of -12.004 mm and 17.6599 mm, respectively, and are used for reflecting light so that the light is finally imaged on the detector.

5. The stereoscopic imaging optical system for a small civilian-oriented unmanned aerial vehicle according to claim 1, characterized by, The air gap between the spherical positive lens (1) and the first double cemented spherical lens (2) is 8.614 mm, the air gap between the first double cemented spherical lens (2) and the diaphragm (3) is 3.462 mm, the air gap between the diaphragm (3) and the second double cemented spherical lens (4) is 0.168 mm, the air gap between the second double cemented spherical lens (4) and the convex spherical mirror (6) in the mirror group is 18.012 mm, and the mirror group is composed of the convex spherical mirror (6) and the concave parabolic mirror (5).

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