Linear array push-broom imaging spectrum system based on optical fiber device

Abstract

The invention relates to a linear array push-broom imaging spectrum system based on an optical fiber device, which comprises a spectrograph, an objective lens and an optical switch, and is characterized in that the view field of a telescope objective is fully utilized, and a second optical fiber of a linear array is coupled to the focal plane of the objective lens to fill the one-dimensional view field of the objective lens. The second optical fiber is connected with the optical switch, the on-off of the sub optical fibers corresponding to different view fields is rapidly controlled through the optical switch, and the flight motion of the aerial carrier platform is matched, so that rapid time-sharing detection based on different view fields of the same high-speed spectrometer can be realized, and an imaging spectrum detection effect similar to push-broom imaging detection can be realized. Compared with a conventional linear array sweep imaging spectrum system, the optical fiber array and the optical switch device are adopted to replace a sweep mechanism, sweep mechanical moving parts are not needed, the size and the weight of the imaging spectrum system are greatly reduced, and the influence on the flight stability of an aerial carrier platform is extremely small.

Description

Technical Field

[0001] The present invention relates to the field of spectral imaging instruments, and in particular to a linear array push-scanning imaging spectral system based on optical fiber devices. Background Art

[0002] Spectral measurement and analysis technology has become a basic technology in studying the composition and structure of materials, and spectral imaging technology combined with imaging function can simultaneously obtain the spatial information and spectral information of the target. It has become an important research direction in the field of optical remote sensing technology. It has been widely and deeply applied and studied in many fields such as resource exploration, agricultural and forestry remote sensing, water remote sensing, disaster monitoring and deep space exploration.

[0003] According to their imaging principles, spectral imaging instruments can be divided into two categories: swing-scan type and push-scan type. The swing-scan imaging spectrometer uses the aircraft's along-track flight to obtain the field of view in the flight direction, obtains the field of view perpendicular to the flight track through mechanical scanning imaging, and uses linear or planar array detectors to receive spectral data of each band; the push-scan imaging spectrometer only obtains the field of view in the flight direction through the aircraft's along-track flight, and uses a large planar array detector to realize the collection of spectral information in the cross-track direction.

[0004] Figure 1 The figure shows the structural principle of a typical push-broom imaging spectrometer. Generally speaking, under the same indicators, the main advantages of a push-broom imaging spectrometer are high imaging detection efficiency, and the system does not require swinging motion. Its structure is relatively simple and its volume is small. At the same time, the characteristics of simultaneously acquiring pixels in the cross-track direction also reduce the difficulty of image stitching. However, the field of view of a push-broom imaging spectrometer is limited by the size of the array detector, and the large array detector is very expensive. Therefore, it is not easy to achieve large field of view detection. In addition, the instrument calibration of a push-broom imaging spectrometer is relatively difficult, and there is also the phenomenon of spectral bending. In contrast, the swing-sweep imaging spectrum system has a relatively complex structure, low detection efficiency, and the swing motion control is relatively complex compared to the image stitching process. However, it has the advantages of large field of view and low cost, and has great application potential in the field of unmanned aerial vehicle imaging spectrum remote sensing.

[0005] According to the different detectors used, the swing-scan imaging spectroscopy system can be divided into linear array swing-scan (refer to Figure 2 ) and area array scanning (reference Figure 3 ). The mechanical scanning part and the spectroscopic detection part of the area array swing scanning imaging spectrometer are similar to those of the linear array swing scanning, such as Figure 3 Shown is the schematic diagram of the area array swing scanning imaging spectrometer. Compared with the linear array swing scanning imaging method, the scanning speed of the swing scanning mechanism of the area array swing scanning method is lower, thereby reducing the difficulty of designing, assembling and controlling the swing scanning mechanism, and the single integration time is longer.

[0006] At present, the linear array swing-scanning imaging spectral system has the advantages of low device cost and large field of view due to its detection principle, but it also has the disadvantages of requiring a swing-scanning mechanism, complex system, low detection efficiency and complex image processing; while the area array push-scanning system has the advantages of relatively simple structure, high scanning efficiency and high resolution, but the area array photoelectric detectors, especially high-performance area array photoelectric detectors in special bands such as ultraviolet and infrared, are expensive, resulting in the problem of high cost of the area array push-scanning spectral imaging system.

[0007] Therefore, the prior art still has deficiencies and needs further improvement. Summary of the invention

[0008] An embodiment of the present invention provides a linear array push-sweep imaging spectroscopy system based on optical fiber devices. To address the above problem, the present invention adopts an optical fiber array and an optical switch device to replace the swing-sweep mechanism, so that the present application does not require swing-sweep mechanical moving parts, greatly reducing the volume and weight of the imaging spectroscopy system, and having little impact on the flight stability of the carrier platform.

[0009] To at least solve the technical problem of untimely handling of equipment failures.

[0010] According to an embodiment of the present invention, a linear array push-scan imaging spectroscopy system based on optical fiber devices is provided, comprising the following steps:

[0011] A spectrometer, used for scanning and detecting the field of view;

[0012] An objective lens, connected to the spectrometer, for directly scanning the field of view;

[0013] An optical switch, one end of which is connected to the spectrometer via a first optical fiber, and the other end of which is connected to the objective lens via a second optical fiber of a linear array;

[0014] The second optical fiber is composed of a plurality of sub-optical fibers arranged in an array or in parallel, and the second optical fiber is coupled to the focal plane of the objective lens, and each sub-optical fiber is used to correspond to a field of view; the length direction of the second optical fiber instrument is parallel to the objective lens, so that the linear array push-scan imaging spectral system obtains the field of view in the flight direction of the flight equipment, and realizes the spectral information collection in the cross-track direction;

[0015] The optical switch switches the field of view through the second optical fiber to achieve time-sharing scanning of multiple fields of view of the spectrometer, thereby improving the scanning efficiency of the imaging spectrometer system.

[0016] Preferably, adjacent sub-optical fibers are arranged in a one-dimensional seamless connection.

[0017] Preferably, the second optical fibers are arranged in double rows in a staggered manner.

[0018] Preferably, the corresponding viewing angles between the sub-optical fibers are relatively fixed.

[0019] Preferably, the linear array push-scan imaging spectroscopy system further comprises:

[0020] The detector is connected to the spectrometer and is used to obtain the spectral data of each band received by the spectrometer.

[0021] Preferably, the detector is a linear array detector.

[0022] Preferably, the optical switch is any one of switches based on mechanical, micro-electromechanical, thermo-optical, electro-optical, magneto-optical and acousto-optic principles.

[0023] Preferably, the optical switches are arranged in a plurality, and the plurality of optical switches correspond to the sub-optical fibers one by one.

[0024] Preferably, the objective lens is a double cemented or triple separated achromatic objective lens.

[0025] The linear array push-scanning imaging spectroscopy system based on optical fiber devices in the embodiment of the present invention makes full use of the field of view of the telescope objective lens itself, couples the second optical fiber of the linear array to the focal plane of the objective lens, and fills the one-dimensional field of view of the objective lens. The second optical fiber is connected to an optical switch, and the optical switch quickly controls the on and off of the sub-optical fibers corresponding to different fields of view. In conjunction with the flight movement of the carrier platform, fast time-sharing detection based on different fields of view of the same high-speed spectrometer can be achieved to achieve an imaging spectroscopy detection effect similar to that of push-scanning imaging detection. Compared with the conventional linear array swing-scanning imaging spectroscopy system, the present invention uses an optical fiber array and an optical switch device to replace the swing-scanning mechanism, does not require a swing-scanning mechanical moving part, greatly reduces the volume and weight of the imaging spectroscopy system, and has minimal impact on the flight stability of the carrier platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 It is a schematic diagram of the structure of a typical push-broom hyperspectral imager in the prior art;

[0028] Figure 2 It is the linear array swing scanning structure principle of a typical swing scanning hyperspectral imager in the prior art;

[0029] Figure 3 It is the structural principle of the typical sweeping hyperspectral imager in the prior art.

[0030] Figure 4 It is a schematic structural diagram of a linear array push-scan imaging spectroscopy system based on optical fiber devices of the present invention;

[0031] Figure 5 Schematic diagram of the single push-scan coverage of ground pixels and improvement of detection efficiency of the present invention.

[0032] Description of the drawings: 1-spectrometer, 2-optical switch, 3-objective lens, 4-first optical fiber, 5-second optical fiber, 6-detector. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] See also Figure 4 and Figure 5 According to an embodiment of the present invention, a linear array push-scan imaging spectroscopy system based on optical fiber devices is provided, which is applied to field scanning of flight equipment, and includes:

[0036] Spectrometer 1, used for detecting spectral signals of each field of view;

[0037] The objective lens 3 is connected to the spectrometer 1 and is used to collect the light energy of the target scene and couple it into the second optical fiber so as to scan the field of view;

[0038] An optical switch 2, one end of which is connected to the spectrometer 1 via a first optical fiber 4, and the other end of which is connected to the objective lens 3 via a second optical fiber 5 of a linear array;

[0039] The second optical fiber 5 is composed of a plurality of sub-optical fibers arranged in an array or in parallel, and the second optical fiber 5 is coupled to the focal plane of the objective lens 3, and each sub-optical fiber is used to correspond to a field of view; the length direction of the second optical fiber 5 is parallel to the objective lens 3, so that the linear array push-scan imaging spectral system obtains the field of view in the flight direction of the flight equipment, and realizes the spectral information collection in the cross-track direction;

[0040] The optical switch 2 switches the field of view through the second optical fiber 5 to achieve time-sharing scanning of multiple fields of view of the spectrometer 1 , thereby improving the scanning efficiency of the spectrometer 1 .

[0041] The linear array push-scanning imaging spectroscopy system based on optical fiber devices in the embodiment of the present invention makes full use of the field of view of the telescope objective lens 3 itself, couples the second optical fiber 5 of the linear array to the focal plane of the objective lens 3, and fills the one-dimensional field of view of the objective lens 3. The second optical fiber 5 is connected to the optical switch 2, and the optical switch 2 quickly controls the on and off of the sub-optical fibers corresponding to different fields of view. In conjunction with the flight movement of the carrier platform, fast time-sharing detection based on different fields of view of the same high-speed spectrometer 1 can be achieved to achieve an imaging spectral detection effect similar to push-scanning imaging detection. Compared with conventional linear array swing-scanning imaging spectroscopy systems, the present invention uses optical fiber arrays and optical switches 2 devices to replace the swing-scanning mechanism, eliminates the need for swing-scanning mechanical moving parts, greatly reduces the volume and weight of the imaging spectroscopy system, and has minimal impact on the flight stability of the carrier platform. See. Figure 5 , which is a display of the bottom surface pixel coverage effect corresponding to multiple lines of push scanning.

[0042] In one embodiment, reference Figure 4 , adjacent sub-fibers are arranged in a one-dimensional seamless connection. Specifically, Figure 4 The dotted box in the middle is a schematic diagram of the principle of the linear array push-scanning imaging spectroscopy system based on optical fiber devices of the present invention. Among them, the optical fiber array is arranged in a one-dimensional seamless form. Since the optical fiber has an outer cladding, the "one-dimensional seamless" arrangement needs to be achieved by staggered splicing. The linear array fiber array is coupled to the focal plane of the telescope objective 3. The on-off switching between each optical fiber and the spectrometer 1 is quickly controlled by the optical switch 2, so that the one-dimensional field of view corresponding to the linear array fiber array can be quickly traversed to complete the push-scanning imaging process of a row of targets. With the forward flight movement of the airborne platform (flight equipment), large-scale linear array push-scanning imaging spectroscopy detection can be completed.

[0043] To specifically illustrate the beneficial effects of the present invention, the following compares the detection efficiency differences between the present invention and the traditional swing-scanning spectral imaging system at the same spatial resolution and spectral resolution levels to demonstrate the improvement in the imaging spectral detection efficiency of the present invention.

[0044] The UAV platform is designed to fly at an altitude of 100m, with a ground resolution of 1m, a maximum swing speed of 90° / s, and a scanning overlap rate of 40% in both directions. The swing-scanning spectral imaging system measures a spectral range of 1-2.5μm, a spectral resolution of 12.5nm, and an F number of 4; the slit size of the spectrometer 1 used at this time is 0.05×0.25mm, the optical system efficiency of the spectrometer 1 is 0.48, and the average quantum efficiency of the long-array InGaAs photodetector 6 is set to 0.85. On a sunny day, with a ground albedo of 0.3 and an exposure time of 5ms, the signal-to-noise ratio of the analytical imaging spectral system at a wavelength of 2.4μm is about 91, which can meet the use requirements. At this time, the corresponding UAV's flight speed is about 0.36m / s.

[0045] Under the same UAV platform, the same spectrometer 1 and spatial resolution, when the solution of the present invention is adopted, a total of 59 optical fibers are required to cover a 30° spatial field of view (10% field of view overlap between optical fibers). At this time, the exposure time of a single frame is 5ms, the switching time of the optical switch 2 is 2ms, and a single-line field of view scan requires a total of (5+2)*59=413ms; during the scanning time of one line, the UAV flies forward 1*0.6=0.6m (40% field of view overlap), and the flight speed is 0.6 / 0.413=1.45m / s.

[0046] Obviously, compared with the conventional solution, at the same spatial / spectral resolution level, the scanning efficiency of the solution of the present invention is more than 4 times that of the traditional solution, and there is no need for mechanical rotation of the scanning device, which reduces the volume and weight of the linear array swing scanning imaging spectroscopy system.

[0047] In one embodiment, reference Figure 4 , the linear array push-scan imaging spectroscopy system also includes:

[0048] The detector 6 is connected to the spectrometer 1 and is used for acquiring the spectral data of each waveband received by the spectrometer 1 .

[0049] Specifically, compared with a short-wave infrared array push-scan imaging spectroscopy system with the same resolution, the present invention uses a linear array InGaAs photodetector 6 instead of a planar array detector 6, so its cost can be reduced by several times or even more than ten times, thus having a greater cost advantage over the planar array push-scan imaging spectroscopy system. The photodetector 6 of the present application can be a linear array detector 6.

[0050] In one embodiment, reference Figure 4 , the second optical fibers 5 are arranged in double rows in an interlaced manner. In other embodiments, in addition to the above-mentioned double row interlaced arrangement, the arrangement of the optical fiber array can also be replaced with other forms, as long as the optical fibers can fill the one-dimensional field of view "without gaps".

[0051] In one embodiment, reference Figure 4Compared with the conventional linear array swing scanning imaging spectroscopy system, the relative position of each optical fiber in the linear array optical fiber array of the present invention is fixed, that is, the corresponding field of view angle of each optical fiber is relatively fixed during push scanning sampling; compared with the conventional linear array swing scanning imaging spectroscopy system, the field of view angle error during measurement of different fields of view is greatly reduced, thereby reducing the difficulty of image stitching processing and improving the image geometric stitching accuracy.

[0052] In one embodiment, reference Figure 4 The optical switch 2 device can be selected in a variety of forms. From the implementation principle of the optical switch 2, the present application can adopt any one of the various optical switches 2 based on the principles of mechanical, micro-electro-mechanical device (MEMS) and thermo-optic, electro-optic, magneto-optic and acousto-optic.

[0053] In one embodiment, reference Figure 4 , from the form of the optical switch 2, there can be 1 to 1, 1 to N, M to N and other forms of optical switches 2. According to the different requirements of the actual system parameters, these optical switches 2 may be used in different imaging spectroscopy systems. The optical switches 2 of the present application are set to be several, and the several optical switches 2 correspond to the sub-fibers one by one. The second optical fiber 5 of the present application is composed of seven sub-fiber arrays or parallel arrangements.

[0054] The present application couples several sub-fibers to the focal plane of the objective lens 3 to correspond to multiple fields of view, and then switches between the sub-fibers through the optical switch 2, thereby realizing rapid switching of the sub-fibers of each field of view. Specifically, the specific implementation form of the objective lens 3 can be flexibly selected according to the specific system design indicators. The present application adopts a double-glued or three-separated achromatic objective lens to well guarantee the imaging quality of the near-axis field of view.

[0055] The present invention uses an optical fiber array to transmit images, and controls the on and off of optical fibers corresponding to different fields of view through an optical switch 2. In combination with a high-speed spectrometer 1, time-sharing fast linear array push-scan imaging spectrum detection based on a single spectrometer 1 can be realized. Compared with the traditional linear array swing-scan spectrum imaging system, the system of the present application has the following advantages:

[0056] 1. Compared with the conventional linear array swing-sweep imaging spectroscopy system, it does not require swing-sweep mechanical moving parts, greatly reducing the volume and weight of the imaging spectroscopy system, and has little impact on the flight stability of the carrier platform.

[0057] 2. The present invention adopts an optical switch 2 to replace the swing scanning mechanical structure to realize detection of different fields of view. The detection efficiency is determined by the integration time of the spectrometer 1 and the switching speed of the optical switch 2. Under the same conditions, the detection efficiency is much higher than that of the existing linear array swing scanning imaging spectroscopy system.

[0058] 3. Compared with the conventional linear array swing scanning imaging spectroscopy system, the relative position of each optical fiber in the linear array optical fiber array of the present invention is fixed, that is, the corresponding field of view angle of each optical fiber is relatively fixed during push scanning sampling; compared with the conventional linear array swing scanning imaging spectroscopy system, the field of view angle error during measurement of different fields of view is greatly reduced, thereby reducing the difficulty of image stitching processing and improving the image geometric stitching accuracy.

[0059] 4. Compared with the conventional planar array push-scan imaging spectroscopy system, the photoelectric detector 6 of the present invention can adopt a linear array detector 6, which has a very obvious low-cost advantage.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A linear array push-broom imaging spectroscopy system based on optical fiber devices, applied to field scanning of flight equipment, characterized in that: include: A spectrometer for detecting the field of view; an objective lens, connected to the spectrometer, for scanning the field of view; An optical switch, one end of which is connected to the spectrometer via a first optical fiber, and the other end of which is connected to the objective lens via a second optical fiber of a linear array; The second optical fiber is composed of a plurality of sub-optical fibers arranged in an array or in parallel, and the second optical fiber is coupled to the focal plane of the objective lens, and each of the sub-optical fibers is used to correspond to a field of view; the length direction of the second optical fiber instrument is parallel to the objective lens, so that the linear array push-scan imaging spectroscopy system obtains the field of view in the flight direction of the flight equipment, and realizes the collection of spectral information in the cross-track direction; The optical switch switches the field of view through the second optical fiber to achieve time-sharing scanning of multiple fields of view of the spectrometer, thereby improving the scanning efficiency of the imaging spectrometer system.

2. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: Adjacent sub-optical fibers are arranged in a one-dimensional seamless connection.

3. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The second optical fibers are arranged in double rows in a staggered manner.

4. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The corresponding viewing angles between the sub-optical fibers are relatively fixed.

5. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The linear array push-scan imaging spectroscopy system also includes: The detector is connected to the spectrometer and is used to obtain and receive spectral data of each waveband of the spectrometer.

6. The linear array push-scanning imaging spectroscopy system based on optical fiber devices according to claim 5, characterized in that: The detector is a linear array detector.

7. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The optical switch is any one of switches based on mechanical, micro-electromechanical, thermo-optical, electro-optical, magneto-optical and acousto-optic principles.

8. The linear array push-scanning imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The optical switches are arranged in a plurality, and the plurality of optical switches correspond to the sub-optical fibers one by one.

9. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The second optical fiber is composed of seven sub-optical fibers arranged in an array or in parallel.

10. The linear array push-scan imaging spectroscopy system based on optical fiber devices according to claim 1, characterized in that: The objective lens is a double-cemented or triple-separated achromatic objective lens.

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