CN107728130B - Multi-channel wide-amplitude synthetic aperture laser imaging radar transmitting and receiving system - Google Patents

Abstract

A multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system, the launch system is composed of a laser light source, a frequency modulator, an arbitrary waveform generator, a fiber beam splitter, a fiber amplifier group, a fiber array, a lens, and a first beam splitter , Brewster prism beam reducer, the receiving system consists of a second beam splitter, a receiving lens, an array detector, an acquisition card and a computer. The present invention increases the amplitude of the optical toe and the imaging strip on the target surface by means of multiple input and multiple output, which is of great significance to the long-distance high-resolution airborne synthetic aperture laser imaging radar.

Description

Multi-channel wide-amplitude synthetic aperture lidar imaging radar transceiver system

technical field

The invention relates to a synthetic aperture laser imaging radar, in particular to a multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system, which is of great significance to an airborne synthetic aperture laser imaging radar with long-distance high resolution and wide stripe amplitude.

Background technique

Synthetic Aperture Imaging Ladar (SAIL) is the only optical imaging observation method that can obtain centimeter-level imaging resolution at long distances. SAR for short) principle, in contrast, the wavelength of light waves is about 3-6 orders of magnitude smaller than the wavelength of microwaves, which brings the resolution of SAIL 3-6 orders of magnitude higher than that of SAR. Fields are 2-5 orders of magnitude smaller. At present, the maximum imaging field of airborne SAIL achieved at home and abroad is 4.8mrad, which is much smaller than the field of view of SAR and CCD cameras (Lu Zhiyong, Zhou Yu, Sun Jianfeng, Luan Zhu, Wang Lijuan, Xu Qian, Li Guangyuan, Zhang Guo, Liu Liren. Airborne Direct-Looking Synthetic Aperture Lidar Imaging Radar Field and Flight Experiment [J]. China Laser, 2017, 44(01): 265-271.).

The prior art (Yu Tang, Bao Qin, Yun Yan, and Mengdao Xing, "Multiple-input multiple-output synthetic aperture ladar system for wide-swath with highazimuth resolution," Appl. Opt. 55, 1401-1405 (2016)) proposed A multi-transmit and multi-receive SAL system in azimuth is proposed, which uses multi-channel data synthesis in azimuth to solve the contradiction between high resolution in azimuth and bandwidth in range mapping. However, this scheme does not provide a transceiver device for synthetic aperture lidar with multiple transmissions and multiple receptions, and does not consider the influence of the duty ratio between the cladding and the core of the transmitting fiber in the transmitting optical path on the far-field imaging.

In the multi-transmit and multi-receive SAIL transmitting device, a plurality of light beams are simultaneously emitted as the emission optical path of the multi-transmission and multi-receive SAIL, and the emitted light is output through the optical fiber. If the transmitting fibers of SAIL with multiple transmissions and multiple receptions are arranged in a direction perpendicular to the along-track direction, due to the existence of the fiber cladding, the target surface is not fully irradiated in the cross-track direction. With tape scanning, the resulting image is only a separate partial picture of the object.

In view of the above problems, we have carried out research on multi-channel wide-amplitude synthetic aperture lidar imaging radar transceiver system. This will be of great significance to the long-range high-resolution wide-stripe range airborne synthetic aperture LiDAR.

SUMMARY OF THE INVENTION

The purpose of the present invention is to further develop the synthetic aperture laser imaging radar, and propose a multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system. The characteristic of this system is that it increases the amplitude of the optical toe and imaging strip of the target surface by means of multiple input and multiple output, and considers the duty cycle between the cladding and the core of the transmitting fiber in the transmitting optical path for far-field imaging The influence of , the inclined arrangement scheme of the fibers in the fiber array is given. In addition, for coherent detection systems, the receiving field of view is restricted by the antenna law, and the receiving aperture is inversely proportional to the field of view. In order to improve the receiving resolution and reduce the power consumption of the system, it is usually desirable to use a large aperture to receive. In order to solve the contradiction between the receiving aperture and the field of view, the present invention uses the array heterodyne receiving method. This will be of great significance for long-range high-resolution airborne synthetic aperture LiDAR.

The technical solution of the present invention is as follows:

A multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system, including a transmitting system and a receiving system, is characterized in that:

The transmitting system includes a laser light source, a frequency modulator, an arbitrary waveform generator, a fiber beam splitter, a fiber amplifier group, a fiber array device, a lens, a first beam splitter, and a Brewster prism beam reducer, and the receiving system consists of: the second beam splitter, the array detector, the acquisition card and the computer; the output end of the laser light source is connected to the first input end of the frequency modulator, and the output end of the arbitrary waveform generator is connected to the The second input end of the frequency modulator is connected to the second input end of the frequency modulator, the output end of the frequency modulator is connected to the input end of the fiber beam splitter, the first output end and the second output end of the fiber beam splitter , the third output end...the nth output end is respectively connected with the input end of the first fiber amplifier, the input end of the second fiber amplifier, the input end of the third fiber amplifier in the said fiber amplifier group...the nth fiber amplifier The output end of the first fiber amplifier, the output end of the second fiber amplifier, the output end of the third fiber amplifier...the output end of the nth fiber amplifier are respectively connected with the output end of the The first input end, the second input end, the third input end...the nth input end of the fiber array device are connected, the output end of the fiber array device is connected with the input end of the lens, and the lens The output end is connected with the input end of the first beam splitter; the first output end of the first beam splitter is connected with the input end of the Brewster prism beam reducer, the Brewster prism The signal output by the output end of the beam reducer is the transmission signal, and the n is a positive integer greater than 3;

The receiving system consists of a receiving lens, a second beam splitter, an array detector, an acquisition card and a computer; the echo signal after the transmitted signal passes through the target surface enters the input end of the receiving lens, and the receiving lens The output end is connected to the first input end of the second beam splitter, the second output end of the first beam splitter is connected to the second input end of the second beam splitter, the The output end of the second beam splitter is connected to the input end of the array detector, the output end of the array detector is connected to the input end of the acquisition card, and the output end of the acquisition card is connected to the input end of the acquisition card. The input end of the computer is connected.

The Brewster prism beam reducer is composed of a first cylindrical wedge mirror and a second cylindrical wedge mirror;

The light from the core of the optical fiber in the optical fiber array device must partially overlap in the cross-track direction at the far field and meet the maximum imaging strip amplitude to ensure that the target is fully irradiated. Influence of duty cycle between cladding and core on far-field imaging. The diameter of each fiber in the fiber array is D, the core diameter is d, the numbers of n fibers are: f ₁ , f ₂ , .., f _n , the intersection of the two adjacent fibers with subscripts. The spacing value dr in the track direction is fixed, which is η times the core diameter, where 0<η<1, and the n transmitting fibers in the fiber array 6 are arranged in the following arrangement: two adjacent fibers The tangent between them is maintained, the arrangement L of the transmitting fibers is L=(f ₁ , f ₂ , .., f _n ), and the angle θ between the line connecting the centers of the n fibers and the horizontal line satisfies the following relationship:

The arrangement of the emitting fibers in the fiber array can ensure that the emitted light partially overlaps in the cross-track direction at the far field under the condition that the maximum imaging strip amplitude is satisfied, so that the target can be completely imaged.

The number of the array elements of the array detector is the same as that of the transmitting fibers of the optical fiber arrayer, and the arrangement is the same. Each array element is closely connected, and the connection line between the centers of the n array elements and the horizontal line The included angle θ satisfies the following relationship:

In addition, since the signal light passes through the Brewster prism beam reducer after being collimated by the emission lens, near-field compression and far-field beam expansion in the cross-orbit direction are realized. How many times the corresponding cross-track upward near field is compressed, the far field will be expanded by the same multiple, and the array detector's cross-track detection field of view is also increased by a corresponding multiple. Assuming that the receiving aperture is a times the transmitting aperture, and the compression ratio of the Brewster prism beam reducer is b, then the unit array element of the corresponding single transmitting fiber on the detection surface of the array detector is in the on-track direction and The relationship of the array on the cross track is: a×ab.

The light reflected by the first beam splitter in the transmitting system is used as the local oscillator light for receiving the echo signal, and the n beams of light in the local oscillator light respectively correspond to each channel in the cross-track direction in the array detector, The local oscillator light and the echo signal reflected from the target surface are received by the array detector for heterodyne reception.

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

1. The present invention increases the amplitude of the optical toe and the imaging strip on the target surface by means of multiple input and multiple output, and expands the field of view.

2. The present invention considers the influence of the duty ratio between the cladding and the core of the transmitting optical fiber in the optical fiber array on far-field imaging, and provides an inclined arrangement scheme of the optical fibers in the optical fiber array. The arrangement of the launch fibers can ensure that when the target is imaged, it is the complete image of the target, rather than a discrete partial picture.

3. The present invention uses the array heterodyne receiving method, which solves the contradiction between the receiving aperture and the field of view in the coherent detection system, and further expands the imaging field of view.

Description of drawings

FIG. 1 is a schematic structural diagram of a multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system according to the present invention.

FIG. 2 is a schematic structural diagram (n=16) of the optical fiber arrangement in the optical fiber array in the multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system of the present invention.

3 is the imaging of the light emitted by the optical fiber array device in the far-field (n=16) in the multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system of the present invention, (a) a schematic diagram of far-field imaging, (b) far-field imaging Projection on the intersection.

FIG. 4 is an arrangement diagram of array elements in an array detector in a multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system according to the present invention (n=4).

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention should not be limited by this.

FIG. 1 is a schematic structural diagram of a multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system according to the present invention. As can be seen from the figure, the multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system of the present invention includes a transmitting system and a receiving system,

The transmitting system includes a laser light source 1, a frequency modulator 2, an arbitrary waveform generator 3, a fiber beam splitter 4, a fiber amplifier group 5, a fiber array device 6, a transmitting lens 7, a first beam splitter 8 and Brewster. Prism reducer 9;

The output end of the laser light source 1 is connected with the first input end of the frequency modulator 2, the output end of the arbitrary waveform generator 3 is connected with the second input end of the frequency modulator 2, The output end of the frequency modulator 2 is connected to the input end of the fiber beam splitter 4, and the first output end, the second output end, the third output end, ... , the nth output end is respectively connected with the input end of the first fiber amplifier 51 in the fiber amplifier group 5, the input end of the second fiber amplifier 52, the input end of the third fiber amplifier 53, ..., the nth fiber amplifier The input ends of 5n are connected, the output end of the first fiber amplifier 51, the output end of the second fiber amplifier 52, the output end of the third fiber amplifier 53, ..., the nth fiber amplifier 5n in the fiber amplifier group 5 The output ends are respectively connected with the first input end, the second input end, the third input end, ..., the nth input end of the optical fiber array device 6, and the output light of the optical fiber array device 6 passes through the The lens 7 and the first beam splitter 8, the first beam splitter 8 divides the incident light into transmitted light and reflected light, and the transmitted light is output through the Brewster prism beam reducer 9 That is, the transmit signal, and the n is a positive integer above 3;

The receiving system is composed of receiving lens 10, second beam splitter 11, array detector 12, acquisition card 13 and computer 14;

The echo signal of the transmitting signal reflected by the target surface passes through the receiving lens 10, passes through the second beam splitter 11, and the reflected light from the first beam splitter 8 passes through the The second beam splitter 11 is reflected into the array detector 12 , and the output end of the array detector 12 is connected to the input end of the computer 14 via the acquisition card 13 .

The multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system is characterized in that the Brewster prism beam reducer 9 is composed of a first cylindrical wedge mirror 91 and a second cylindrical wedge mirror 92;

The light from the core of the optical fiber in the optical fiber array device 6 must partially overlap in the cross-track direction at the far field and meet the maximum imaging strip amplitude to ensure that the target is fully irradiated. The effect of the duty cycle between the cladding and the core on far-field imaging. The diameter of each fiber of the fiber array 6 is D, the diameter of the core is d, the numbers of the n fibers are respectively: f ₁ , f ₂ , .., f _n , the subscripts of the two adjacent fibers are The spacing value dr in the cross-track upward direction is fixed, which is η times the diameter of the fiber core, where 0<η<1, and the n transmitting fibers of the fiber array 6 are arranged in the following arrangement: two adjacent fibers The tangent between them is maintained, the arrangement L of the transmitting fibers is L=(f ₁ , f ₂ , .., f _n ), and the angle θ between the line connecting the centers of the n fibers and the horizontal line satisfies the following relationship:

The arrangement of the emitting fibers in the fiber array 6 can ensure that the emitted light in the far-field cross-track direction partially overlaps under the condition that the maximum imaging strip amplitude is satisfied, so that the target can be completely imaged.

The number of the array elements of the array detector 12 is the same as that of the transmitting fibers of the fiber array device 6, the arrangement is the same, each array element is closely connected, and the connection line between the centers of the n array elements and the horizontal line The included angle θ between them satisfies the following relationship:

In addition, since the signal light passes through the Brewster prism beam reducer 9 after being collimated by the lens, near-field compression and far-field beam expansion in the cross-track direction are realized. How many times the corresponding cross-track upward near field is compressed, the far field will be expanded by the same multiple, and the cross-track detection field of the array detector 12 is also increased by the corresponding multiple. Assuming that the receiving aperture is a times the transmitting aperture, and the compression ratio of the Brewster prism beam reducer 9 is b, then the unit array element of the single transmitting optical fiber corresponding to the detection surface of the array detector 12 is on the track. The array relationship between the direction and the cross track is: a×ab.

In the transmitting system, the light reflected by the first beam splitter 8 is used as the local oscillator light for receiving the echo signal, and the n beams of light in the local oscillator light respectively correspond to each of the array detectors 12 in the cross-track direction. The array element, the local oscillator light and the echo signal reflected from the target surface are received by the array detector 12 heterodyne, and the signal received by the array detector 12 heterodyne is sent to the The computer 14 performs data processing.

Experiments show that the present invention increases the amplitude of the optical toe and imaging strip of the target surface by means of multiple input and multiple output, and considers the duty ratio between the cladding and the core of the transmitting fiber in the transmitting optical path for far-field imaging The influence of , the inclined arrangement scheme of the fibers in the fiber array is given. In addition, for the coherent detection system, the receiving field of view is restricted by the antenna law, and the receiving aperture is inversely proportional to the field of view. In order to improve the receiving resolution and reduce the power consumption of the system, it is usually desirable to use a large aperture to receive. In order to solve the contradiction between the receiving aperture and the field of view, the present invention uses an array heterodyne receiving method. This will be of great significance for long-range high-resolution airborne synthetic aperture LiDAR.

Claims (2)

1. a multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system, comprising a transmitting system and a receiving system, is characterized in that: The transmitting system comprises a laser light source (1), a frequency modulator (2), an arbitrary waveform generator (3), a fiber beam splitter (4), a fiber amplifier group (5), a fiber array (6), a transmitter a lens (7), a first beam splitter (8) and a Brewster prism beam reducer (9); The output end of the laser light source (1) is connected to the first input end of the frequency modulator (2), and the output end of the arbitrary waveform generator (3) is connected to the frequency modulator (2). ) is connected to the second input end of the frequency modulator (2), the output end of the frequency modulator (2) is connected to the input end of the optical fiber splitter (4), and the first output of the optical fiber splitter (4) end, the second output end, the third output end, ..., the nth output end are respectively connected with the input end of the first fiber amplifier (51) and the second fiber amplifier (52) in the fiber amplifier group (5) The input end of the third fiber amplifier (53), ..., the input end of the nth fiber amplifier (5n) are connected, and the output of the first fiber amplifier (51) in the fiber amplifier group (5) is connected. end, the output end of the second fiber amplifier (52), the output end of the third fiber amplifier (53), ..., the output end of the nth fiber amplifier (5n) are respectively connected with the output end of the fiber array device (6). An input end, a second input end, a third input end, ..., the nth input end are connected, and the output light of the fiber array device (6) enters the first input end through the emission lens (7). A beam splitter (8), the first beam splitter (8) divides the incident light into transmitted light and reflected light, and the transmitted light is outputted by the Brewster prism beam reducer (9), so that the emission signal is output. Said n is a positive integer of 3 or more; The receiving system includes a receiving lens (10), a second beam splitter (11), an array detector (12), an acquisition card (13) and a computer (14); The echo signal reflected by the target surface of the transmitting signal passes through the receiving lens (10), passes through the second beam splitter (11) and communicates with the first beam splitter (8) in sequence. The reflected light enters the array detector (12) after being reflected by the second beam splitter (11), and the output end of the array detector (12) is connected with the acquisition card (13) The input of the computer (14) is connected. 2. The multi-channel wide-amplitude synthetic aperture laser imaging radar transceiver system according to claim 1, wherein the diameter of each fiber in the fiber array device (6) is D, and the core diameter is The numbers of d and n fibers are respectively: f ₁ , f ₂ ,..,f _n , the distance value dr between the two adjacent optical fibers in the cross-track direction is fixed, which is η times the core diameter, where, 0<η<1, the n transmitting fibers in the fiber array device (6) are arranged in the following manner: A tangent is maintained between two adjacent optical fibers, and the arrangement L of the transmitting optical fibers is L=(f ₁ , f ₂ , .., f _n ), and the connection between the centers of the n optical fibers and the horizontal line is The included angle θ satisfies the following relationship:

The array elements of the array detector (12) are the same in number as the transmitting fibers of the optical fiber array device (6), and are arranged in the same manner, and each array element is closely connected, and the center of the n array elements is The angle β between the connecting line and the horizontal line satisfies the following relationship:

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