CN108761553B - Passive millimeter wave dual-channel synchronous imaging system for security inspection and imaging method thereof - Google Patents
Passive millimeter wave dual-channel synchronous imaging system for security inspection and imaging method thereof Download PDFInfo
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- CN108761553B CN108761553B CN201810218653.5A CN201810218653A CN108761553B CN 108761553 B CN108761553 B CN 108761553B CN 201810218653 A CN201810218653 A CN 201810218653A CN 108761553 B CN108761553 B CN 108761553B
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Abstract
The invention discloses a passive millimeter wave dual-channel synchronous imaging system for security inspection and an imaging method thereof, and belongs to the technical fields of millimeter wave imaging, security inspection and the like. The device comprises a smooth metal reflecting surface, a Cassegrain antenna, a radiometer, a longitudinal rotary table, an optical fiber sensor, a horizontal rotary table, a sensor baffle plate, a proximity switch, a data acquisition unit, a computer and a scanning control unit; the smooth metal reflecting surface is fixed on the longitudinal rotary table at an angle of 45 degrees, the longitudinal rotary table and the Cassegrain antenna are coaxially fixed on the horizontal rotary table, a feed source of the Cassegrain antenna is connected with a radiometer, the radiometer is connected with a data acquisition unit, and the data acquisition unit is connected with a computer. The imaging system has the advantages of simple structure, low cost, small volume, low power consumption, high stability and high imaging speed, can effectively detect dangerous articles hidden on a human body, can simultaneously carry out security inspection imaging on detected personnel in security inspection channels on the left side and the right side of the scanning platform, and greatly improves the security inspection efficiency.
Description
Technical Field
The invention belongs to the technical field of millimeter wave imaging, security inspection and the like, relates to an imaging system, and particularly relates to a W-band passive millimeter wave dual-channel synchronous imaging system for human body security inspection.
Background
At present, the security situation is severe, and people put higher requirements on the safety, reliability and intellectualization of a security inspection system. At present, a security inspection department mainly uses an X-ray security inspection instrument to detect contraband articles in luggage, the security inspection detection capability is strong, a perspective image with higher resolution can be obtained, but the ionization effect of X-rays is more harmful to human bodies and cannot be used for detecting the contraband articles hidden on human bodies. Even if there are low radiation doses of X-ray machines currently available, they are still not readily accepted by the public. For example, the essence of the so-called 'weak photon' human body security inspection instrument produced by a certain security company in Anhui is to perform security inspection imaging on a human body by using low-dose X-rays, the instrument is put into use in a DuoDong railway station and a DuoShu international airport in 2016 year and 4 month in sequence, but once relevant experts disclose and report, people are caused to panic immediately, and the instrument is immediately stopped by the national ministry of environmental protection in the form of urgent documents in 2016 year and 10 month.
The metal detector can detect whether a metal object exists on a person, but cannot detect the shape of the metal object, cannot judge whether the metal object is safe metal object, such as metal components in a prosthetic limb, and possibly has a gun hidden therein, cannot distinguish the metal in the prosthetic limb from the gun, and is required to detect the matching of objects, so that the efficiency is too low.
Because passive millimeter wave imaging technology has the advantage of being unique in the aspect of detecting hidden weapons on human bodies, the millimeter wave imaging technology is a research hotspot for security inspection in recent years. The passive millimeter wave imaging technology is used for contrast imaging through millimeter wave radiation energy difference of a detection target, a radiation source is not needed, absolute safety is realized on a human body, and textiles such as clothes have almost no shielding effect on millimeter waves, so that the passive millimeter wave imaging technology is suitable for security inspection imaging on the human body. According to different imaging systems, passive millimeter wave imaging technologies are mainly classified into the following four types:
one is phased array imaging technology, which utilizes electronic scanning instead of mechanical scanning. The phased array antenna is composed of two-dimensional array units, each receiving unit is connected with a phase shifter, and the antenna beam view is realized by controlling the phase and amplitude of the receiving units. The technology has the advantages that the system is small in size, the imaging speed is high, and real-time imaging can be achieved. However, the antenna structure is complex, it is difficult to realize a high-resolution system, and the system is used for passive imaging and is still in the research and development stage.
And secondly, a synthetic aperture imaging technology is adopted, and a plurality of antennas with smaller apertures are combined to simulate the effect of a large-aperture antenna by utilizing a partial coherence principle. For example, NEC corporation of japan developed prototypes based on synthetic aperture imaging, and the german space agency developed imaging systems for Ka-band and W-band synthetic aperture radiometers, both ground-based and airborne, and the like. The technology of the scheme is relatively mature, but a plurality of receiving units are required to form a sparse array, and the design cost and the hardware cost are still high.
And thirdly, a focal plane array imaging technology, which generally adopts a parabolic antenna or a lens antenna for focusing, adopts a plurality of unit antennas distributed on a focal plane and uses a reflecting surface structure to simultaneously image multiple points of a multi-target area. Typical representatives are Vela125, X250, S350, model No. products of Millivision company, USA, PMMW imager model of Lockheed Martin company, focal plane imager of Northrop Grumman company, and the like. The technology can greatly shorten the imaging time, but the system complexity is higher, and a focal plane array is adopted as a receiving unit, and thousands of millimeter wave receiving units are frequently adopted, so that the hardware cost is very expensive, and the technology is difficult to popularize at present.
Fourthly, the traditional mechanical scanning imaging technology is a relatively original millimeter wave radiation imaging mode. In this way, an antenna with a relatively narrow beam width is used as a receiver, and the whole scene is scanned by mechanical motion to acquire an image of the scene. Such as a single-channel scanning imaging system of Millivision corporation, usa, an 8mm band imaging system developed by the national research center for superconducting radio in ukraine, and the like. The common scanning mode mainly adopts row-column scanning, continuous acceleration and deceleration are required in the scanning process, the imaging time is long, and the resolution ratio is low; or an improved mode, namely a mode of one-dimensional electrical scanning and another-dimensional mechanical scanning is adopted, the imaging time is accelerated, but a plurality of receivers are required to be arranged in an array, and the system cost is greatly increased. The system has the advantages of simple principle and relatively low cost, reduces the imaging time if the imaging mode is improved, and is quite applicable to human body security inspection imaging in some occasions without real-time imaging.
Disclosure of Invention
The invention aims to overcome the defects of the existing human body security check mode and provides a W-band passive millimeter wave dual-channel synchronous imaging security check system for human body security check.
The technical problem proposed by the invention is solved as follows:
a W-band passive millimeter wave dual-channel synchronous imaging system for human body security inspection comprises a smooth metal reflecting surface 1, a Cassegrain antenna 2, a radiometer 3, a longitudinal rotary table 4, an optical fiber sensor, a horizontal rotary table 6, a sensor baffle, proximity switches 801 and 802, a data acquisition unit 9, a computer 10 and a scanning control unit 11;
the optical fiber sensors comprise a horizontal optical fiber sensor 501 and a longitudinal optical fiber sensor 502;
the sensor barrier comprises two horizontal sensor barriers 701 and 702, a proximity switch barrier 703 and longitudinal sensor barriers 704 and 705;
the smooth metal reflecting surface 1 and two longitudinal optical fiber sensor blocking pieces 704 and 705 are fixed on the longitudinal turntable 4; the longitudinal rotary table 4 and the Cassegrain antenna 2 are respectively and coaxially fixed on the opposite sides of the horizontal rotary table 6; the two horizontal sensor blocking pieces 701 and 702 and the approach switch blocking piece 703 are fixed on the side surface of the horizontal turntable 6 and are used for controlling the starting and stopping positions of the horizontal turntable and the effective area of the horizontal view field; the smooth metal reflecting surface 1 is fixed on the longitudinal turntable 4 at an angle of 45 degrees, and the center of the smooth metal reflecting surface is aligned with the center of the Cassegrain antenna 2; the feed source of the Cassegrain antenna 2 is fixed on the main reflecting surface of the Cassegrain antenna 2; the input end of the radiometer 3 is connected with the feed source of the Cassegrain antenna 2, and the output end is connected with the data acquisition unit 9; the output end of the data acquisition unit 9 is connected with a computer 10 for data processing and image recovery; the outer sides of the two horizontal sensor blocking pieces 701 and 702 are provided with a horizontal optical fiber sensor 501; the outer sides of the two longitudinal sensor blocking pieces 704 and 705 are provided with a longitudinal optical fiber sensor 502; two proximity switches 801 and 802 are arranged on the outer side of the proximity switch blocking piece 703; the horizontal turntable 6 and the longitudinal turntable 4 are respectively driven by two servo motors controlled by a scanning control unit 11.
The smooth metal reflecting surface 1 reflects millimeter wave energy radiated from each direction of a channel observation scene at two sides to the main reflecting surface of the Cassegrain antenna 2, the Cassegrain antenna 2 focuses on the feed source, and the radiometer 3 connected with the feed source can receive the millimeter wave energy radiated from each wave beam direction of the scene.
The radiometer 3 is a direct detection type W-waveband millimeter wave radiometer, and consists of a first LNA cascade unit 301, a second LNA cascade unit 302, a detector unit 303 and a video amplifier unit 304; the Cassegrain antenna feed source is connected with a first LNA (low-noise amplifier) cascade unit 301, the first LNA cascade unit 301 is connected with a second LNA cascade unit 302, the second LNA cascade unit 302 is connected with a detector unit 303, and the detector unit 303 is connected with a video amplifier unit 304; millimeter wave radiation energy of an observation scene is converged by the Cassegrain antenna 2, amplified by the LNA cascade units 301 and 302, detected by the detector unit/303 and amplified by the video amplifier unit 304, and a voltage signal which is linearly related to the millimeter wave energy radiated by the observation scene is output.
The maximum rotation angle of the horizontal rotary table 4 is 45 degrees, the rotation angle of the longitudinal rotary table is 360 degrees, the longitudinal rotary table rotates at a constant speed, and the longitudinal imaging view field can be flexibly adjusted by controlling the data acquisition time according to the actual target size.
In the scanning imaging process, the two-channel targets to be detected are respectively positioned at two sides of the system. The scanning control unit 11 controls the two servo motors to drive the horizontal rotary table 6 and the longitudinal rotary table 4 to rotate simultaneously according to the set rotating speed, and the horizontal rotary table and the longitudinal rotary table respectively scan the target scene transversely and longitudinally. The horizontal rotary disc 6 is controlled by a servo motor rotating in the horizontal direction, the maximum rotation angle in the horizontal direction is controlled by the proximity switch blocking piece 703 and the two proximity switches 801 and 802 on the horizontal rotary disc, the horizontal rotary disc 6 rotates at a uniform speed, and when the proximity switch blocking piece 703 rotates to the position of the proximity switch 801 or 802, the horizontal rotary disc rotates in the reverse direction, and the reciprocating operation is carried out. During the rotation of the horizontal turntable 6, the two horizontal sensor baffles 701 and 702 sequentially pass through the horizontal optical fiber sensor 501 to generate two pulse signals in sequence, and the start and the end of the acquisition of the target scene image data of the two channels are controlled (the circumferential angles corresponding to the horizontal sensor baffles 701 and 702 are smaller than the circumferential angles corresponding to the two proximity switches 801 and 802). And the acquisition of each line of data in the millimeter wave images of the two channels is realized by carrying out time-delay acquisition on pulse signals generated by the longitudinal optical fiber sensor 502 in the rotation process of the smooth metal reflecting surface 1. When the longitudinal sensor baffle 704 generates a pulse signal through the longitudinal optical fiber sensor 502, the reflecting surface is marked to just scan a first channel target scene, and a row of pixel data at a corresponding position in the channel target scene is obtained through delayed acquisition of the data acquisition unit; similarly, when the longitudinal sensor baffle 705 generates a pulse signal through the longitudinal optical fiber sensor 502, the reflecting surface is marked to just scan a second channel target scene, and a row of pixel data at a corresponding position in the channel target scene is obtained through delayed acquisition by the data acquisition unit, wherein the delay time is less than the interval of the pulse signals generated by the two longitudinal optical fiber sensors. Therefore, each time the smooth metal reflecting surface 1 rotates for one circle, the data acquisition unit acquires a column of pixel data of the corresponding position in the target scenes on the two sides. Because the horizontal rotary table 6 and the longitudinal rotary table 4 rotate at a constant speed, each row of collected data corresponds to a row of pixel points which are equal in height, aligned and parallel in the target scene. And finally transmitting the data acquired by the data acquisition unit to a computer for corresponding processing such as data separation, turning and the like to respectively obtain the double-channel millimeter wave images.
The invention also discloses an imaging method using the imaging system, which comprises the following steps: the smooth metal reflecting surface 1 rotates at a constant speed along the axis, two longitudinal sensor blocking pieces 704 and 705 which rotate together with the smooth metal reflecting surface sequentially pass through the longitudinal optical fiber sensor 502, the data acquisition unit 9 is respectively controlled to acquire data of target scenes of a left channel and a right channel of the system, the acquisition is stopped when the smooth metal reflecting surface 1 rotates away from the target scenes, and the acquisition of data of the next row is started until the next longitudinal optical fiber sensor 502 generates a trigger pulse, the horizontal turntable 6 just rotates by an offset angle in the horizontal direction, and the data acquisition of the whole scene is finished; and performing corresponding algorithm processing according to the acquired data to obtain a gray value or a pseudo-color value of the dual-channel target to be detected, and displaying a millimeter wave image synchronously scanned by the two channels on the computer 10.
The invention has the beneficial effects that:
compared with the prior art that repeated acceleration and deceleration are needed in the translation scanning process, the W-waveband passive millimeter wave dual-channel synchronous imaging system for human body security inspection disclosed by the invention utilizes a direct detection type W-waveband millimeter wave radiometer, does not need a local oscillator, and is small in size and low in power consumption; the system cost and the imaging time are both considered, a two-dimensional turntable spiral scanning mode is adopted, and only a two-dimensional mechanical turntable needs to rotate at a constant speed, so that the mechanical stability is facilitated, and the scanning speed is higher; the two target channels are synchronously scanned, so that the security inspection efficiency is improved in a double way; the system has the advantages of simple structure, high stability and high scanning efficiency, and can effectively and simultaneously detect the hidden dangerous articles on the human body on the two channels.
Drawings
FIG. 1 is a schematic view of a working scenario of the system of the present invention;
FIG. 2 is a block diagram of the overall architecture of the system of the present invention;
FIG. 3 is a schematic side view of the system of the present invention;
FIG. 4 is a schematic top view of the system of the present invention;
FIG. 5 is a schematic diagram of a direct-detection W-band millimeter wave radiometer configuration of the system of the present invention;
FIG. 6 is a schematic diagram of the system of the present invention implementing synchronous scanning of a dual channel target;
FIG. 7 is a schematic diagram of a scan trajectory of a target plane by the system of the present invention;
FIG. 8 is an effect diagram of the system of the present invention for scanning and imaging a target human body carrying a metal gun and a metal knife in two side channels respectively.
Detailed Description
The invention is further described below with reference to the figures and examples.
The embodiment provides a security inspection system for W-band passive millimeter wave dual-channel synchronous imaging for human body security inspection, which is characterized in that a working scene schematic diagram is shown in fig. 1, an overall structure block diagram, a side view schematic diagram and a top view schematic diagram are respectively shown in fig. 2, fig. 3 and fig. 4, and the security inspection system comprises a smooth metal reflecting surface 1, a cassegrain antenna 2, a radiometer 3, a longitudinal rotary table 4, an optical fiber sensor, a horizontal rotary table 6, a sensor baffle, proximity switches 801 and 802, a data acquisition unit 9, a computer 10 and a scanning control unit 11;
the optical fiber sensors comprise a horizontal optical fiber sensor 501 and a longitudinal optical fiber sensor 502;
the sensor barrier comprises two horizontal sensor barriers 701 and 702, a proximity switch barrier 703 and longitudinal sensor barriers 704 and 705;
the caliber of the Cassegrain antenna 2 is 300 mm;
the smooth metal reflecting surface 1 and two longitudinal optical fiber sensor blocking pieces 704 and 705 are fixed on the longitudinal turntable 4; the longitudinal rotary table 4 and the Cassegrain antenna 2 are respectively and coaxially fixed on the opposite sides of the horizontal rotary table 6; the two horizontal sensor blocking pieces 701 and 702 and the approach switch blocking piece 703 are fixed on the side surface of the horizontal turntable 6 and are used for controlling the starting and stopping positions of the horizontal turntable and the effective area of the horizontal view field; the smooth metal reflecting surface 1 is fixed on the longitudinal turntable 4 at an angle of 45 degrees, and the center of the smooth metal reflecting surface is aligned with the center of the Cassegrain antenna 2; the feed source of the Cassegrain antenna 2 is fixed on the main reflecting surface of the Cassegrain antenna 2; the input end of the radiometer 3 is connected with the feed source of the Cassegrain antenna 2, and the output end is connected with the data acquisition unit 9; the output end of the data acquisition unit 9 is connected with a computer 10 for data processing and image recovery; the outer sides of the two horizontal sensor blocking pieces 701 and 702 are provided with a horizontal optical fiber sensor 501; the outer sides of the two longitudinal sensor blocking pieces 704 and 705 are provided with a longitudinal optical fiber sensor 502; two proximity switches 801 and 802 are arranged on the outer side of the proximity switch blocking piece 703; the horizontal turntable 6 and the longitudinal turntable 4 are respectively driven by two servo motors controlled by a scanning control unit 11.
The smooth metal reflecting surface 1 reflects millimeter wave energy radiated from each direction of a channel observation scene at two sides to the main reflecting surface of the Cassegrain antenna 2, the Cassegrain antenna 2 focuses on the feed source, and the radiometer 3 connected with the feed source can receive the millimeter wave energy radiated from each wave beam direction of the scene.
The radiometer 3 is a direct detection type W-band millimeter wave radiometer, and a schematic structural diagram thereof is shown in fig. 5, and is composed of a first LNA cascade unit 301, a second LNA cascade unit 302, a detector unit 303, and a video amplifier unit 304; the feed source of the Cassegrain antenna 2 is connected with a first LNA cascade unit 301, the first LNA cascade unit 301 is connected with a second LNA cascade unit 302, the second LNA cascade unit 302 is connected with a detector unit 303, and the detector unit 303 is connected with a video amplifier unit 304; millimeter wave radiation energy of an observation scene is converged by the Cassegrain antenna 2, amplified by the LNA cascade units 301 and 302, detected by the detector unit/303 and amplified by the video amplifier unit 304, and a voltage signal which is linearly related to the millimeter wave energy radiated by the observation scene is output.
The maximum rotation angle of the horizontal rotary table 4 is 45 degrees, the rotation angle of the longitudinal rotary table is 360 degrees, the longitudinal rotary table rotates at a constant speed, and the longitudinal imaging view field can be flexibly adjusted by controlling the data acquisition time according to the actual target size.
As shown in fig. 1 and fig. 6, in the process of scanning and imaging, the two-channel targets to be measured are respectively located at two sides of the system. The scanning control unit 11 controls the two servo motors to drive the horizontal rotary table 6 and the longitudinal rotary table 4 to rotate simultaneously according to the set rotating speed, and the horizontal rotary table and the longitudinal rotary table respectively scan the target scene transversely and longitudinally. The horizontal rotary disc 6 is controlled by a servo motor rotating in the horizontal direction, the maximum rotation angle in the horizontal direction is controlled by the proximity switch blocking piece 703 and the two proximity switches 801 and 802 on the horizontal rotary disc, the horizontal rotary disc 6 rotates at a uniform speed, and when the proximity switch blocking piece 703 rotates to the position of the proximity switch 801 or 802, the horizontal rotary disc rotates in the reverse direction, and the reciprocating operation is carried out. In fig. 4, a and b are positions of the horizontal turntable which are rotated forward and backward to the maximum angle respectively. During the rotation of the horizontal turntable 6, the two horizontal sensor baffles 701 and 702 sequentially pass through the horizontal optical fiber sensor 501 to generate two pulse signals in sequence, and the start and the end of the acquisition of the target scene image data of the two channels are controlled (the circumferential angles corresponding to the horizontal sensor baffles 701 and 702 are smaller than the circumferential angles corresponding to the two proximity switches 801 and 802). And each line of data in the millimeter wave images of the two channels is acquired in a delayed manner through pulse signals generated by the longitudinal optical fiber sensor in the rotating process of the smooth metal reflecting surface 1. Fig. 6 is a schematic diagram of the two-channel synchronous target scanning realized during each rotation of the longitudinal turntable 4 and the smooth metal reflective surface 1, where O is the center of the longitudinal turntable, d is the horizontal distance from the center of the longitudinal turntable to the target plane, and θ is the longitudinal scanning view angle width of the target plane (determined by the data acquisition time). When the longitudinal sensor baffle 704 generates a pulse signal through the longitudinal optical fiber sensor 502, the reflecting surface is marked to just scan a first channel target scene, and a row of pixel data at a corresponding position in the channel target scene is obtained through delayed acquisition of the data acquisition unit; similarly, when the longitudinal sensor baffle 705 generates a pulse signal through the longitudinal optical fiber sensor 502, it marks that the reflecting surface just scans to a second channel target scene, and a line of pixel data at a corresponding position in the channel target scene is acquired through the data acquisition unit 9 by delay acquisition, wherein the delay time is less than the interval of the pulse signals generated by the two longitudinal optical fiber sensors. Therefore, each time the smooth metal reflecting surface 1 rotates for one circle, the data acquisition unit 9 acquires a column of pixel data of the corresponding position in the target scenes on the two sides. Because the horizontal rotary table 6 and the longitudinal rotary table 4 rotate at a constant speed, each row of collected data corresponds to a row of pixel points which are equal in height, aligned and parallel in the target scene. Fig. 7 is a schematic diagram of the scanning trajectory of the target plane of each channel during each scanning process, wherein the dotted line represents the trajectory of the scanning and data acquisition of the target plane. For example, the time interval of two horizontal sensor baffles 701 and 702 sequentially passing through the horizontal optical fiber sensor 501 is 5s, the width of a target scene at 3m far from both sides is 1m, the rotating speed of the metal reflecting surface is 8r/s, 100 data are acquired by each row of the acquisition card, the height of the target scene at 3m far from is 2m, 40 rows of data are obtained by scanning channels at both sides once, 100 data are acquired in each row, and 40 × 100 data are imaging data of the target scene at 3m far from, 1m wide and 2m high. And finally transmitting the data acquired by the data acquisition unit to a computer for corresponding processing such as data separation, turning and the like to respectively obtain the double-channel millimeter wave images. Fig. 8 is an effect diagram of scanning and imaging two target human bodies carrying metal guns and metal knives standing on the channels on the two sides of the scanning platform respectively.
The embodiment also discloses an imaging method using the imaging system, which comprises the following steps: the smooth metal reflecting surface 1 rotates at a constant speed along the axis, two longitudinal sensor blocking pieces 704 and 705 which rotate together with the smooth metal reflecting surface sequentially pass through the longitudinal optical fiber sensor 502, the data acquisition unit 9 is respectively controlled to acquire data of target scenes of a left channel and a right channel of the system, the acquisition is stopped when the smooth metal reflecting surface 1 rotates away from the target scenes, and the acquisition of data of the next row is started until the next longitudinal optical fiber sensor 502 generates a trigger pulse, the horizontal turntable 6 just rotates by an offset angle in the horizontal direction, and the data acquisition of the whole scene is finished; and performing corresponding algorithm processing according to the acquired data to obtain a gray value or a pseudo-color value of the dual-channel target to be detected, and displaying a millimeter wave image synchronously scanned by the two channels on the computer 10.
The imaging principle of the invention is as follows:
in nature, an object with a temperature higher than absolute zero radiates electromagnetic waves in a self-shooting mode, the energy of the radiated electromagnetic waves is distributed in a wide electromagnetic wave frequency range, wherein in the range that the bandwidth is delta f near the frequency f of the millimeter waves, the energy of the millimeter waves radiated by the object per unit volume is as follows:
wherein the meaning of the physical symbols is:
rho is the emissivity of the object, which is between 0 and 1, the emissivity of the black body is 1, and the emissivity of the metal is 0.
k-Boltzmann constant of 1.38054 × 10-23J/K。
T-the physical temperature of the object.
c-speed of light, 299792458 m/s.
The millimeter wave power radiated by the visible object itself is proportional to the physical temperature of the object. The object not only radiates millimeter wave energy, but also reflects the millimeter wave energy irradiated on the object and transmits the millimeter wave energy radiated by the object behind the object, and the total millimeter wave energy radiated by the object can be generally used as the effective radiation temperature T of the objectETo measure:
TE＝ρT0+rTI+tTB (2)
wherein r is the reflectivity of the object
TI-ambient irradiation temperature
t-transmittance of the object
TBRadiation temperature of the object behind
Objects of different materials exhibit different effective radiation temperatures due to different firing rates, reflectivities, and transmittances. For example, the metal basically reflects the ambient irradiation temperature (ρ ═ 0, r ═ 1), the human body mostly absorbs the millimeter waves (ρ ═ 0.5 to 0.9, r < 0.5), and the clothes mainly allow the millimeter waves to transmit (t ═ 0.6 to 0.9); the passive millimeter wave human body security inspection imaging is realized based on the characteristic.
The radiometer receives the millimeter wave energy radiated by the scene and converts the millimeter wave energy into voltage for output, and the output voltage is as follows:
Vd＝CGRF(Ps+Pm) (3)
wherein G isRFFor LNA cascade unit gain, C for detector sensitivity, PsFor the power of the millimeter-wave signal received by the radiometer, PrnThe noise power of the radiometer itself.
In conclusion, the W-band passive millimeter wave dual-channel synchronous imaging system for human body security inspection provided by the invention takes system cost and imaging time into consideration, and adopts a two-dimensional turntable spiral scanning mode, namely, two horizontal turntables and two longitudinal turntables rotate at a constant speed simultaneously to perform two-dimensional scanning, wherein the longitudinal turntables and the card-type antenna are fixed on the horizontal turntables together with the same axis, and the Cassegrain antenna receives millimeter wave radiation energy of a target scene reflected by a smooth metal plate on the longitudinal turntables and transmits the millimeter wave radiation energy to the millimeter wave radiometer; the direct detection type W-waveband millimeter wave radiometer is used, a local oscillator is not needed, the size is small, and the power consumption is low; and the two target channels are synchronously scanned, so that the security inspection efficiency is improved in a double way. The system has the advantages of simple structure, high stability and high scanning efficiency, and can effectively and simultaneously detect the hidden dangerous articles on the human body on the two channels.
The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.
Claims (4)
1. A W-band passive millimeter wave dual-channel synchronous imaging system for human body security inspection is characterized by comprising a smooth metal reflecting surface (1), a Cassegrain antenna (2), a radiometer (3), a longitudinal rotary table (4), an optical fiber sensor, a horizontal rotary table (6), a sensor baffle, proximity switches (801 and 802), a data acquisition unit (9), a computer (10) and a scanning control unit (11);
the optical fiber sensor comprises a horizontal optical fiber sensor (501) and a longitudinal optical fiber sensor (502);
the sensor flap comprises two horizontal sensor flaps (701, 702), a proximity switch flap (703) and longitudinal sensor flaps (704, 705);
the smooth metal reflecting surface (1) and two longitudinal optical fiber sensor blocking pieces (704, 705) are fixed on the longitudinal turntable (4); the longitudinal rotary table (4) and the Cassegrain antenna (2) are respectively and coaxially fixed on the opposite sides of the horizontal rotary table (6); the two horizontal sensor blocking pieces (701, 702) and the approach switch blocking piece (703) are fixed on the side surface of the horizontal turntable (6); the smooth metal reflecting surface (1) is fixed on the longitudinal turntable (4) at an angle of 45 degrees, and the center of the smooth metal reflecting surface is aligned with the center of the Cassegrain antenna (2); a feed source of the Cassegrain antenna (2) is fixed on a main reflecting surface of the Cassegrain antenna (2); the input end of the radiometer (3) is connected with the feed source of the Cassegrain antenna (2), and the output end of the radiometer is connected with the data acquisition unit (9); the output end of the data acquisition unit (9) is connected with a computer (10) for data processing and image recovery; a horizontal optical fiber sensor (501) is arranged at the outer sides of the two horizontal sensor blocking pieces (701, 702); longitudinal optical fiber sensors (502) are arranged outside the two longitudinal sensor blocking pieces (704, 705); two proximity switches (801, 802) are arranged on the outer side of the proximity switch blocking piece (703); the horizontal rotary table (6) and the longitudinal rotary table (4) are respectively driven by two servo motors controlled by the scanning control unit (11).
2. The W-band passive millimeter wave dual-channel synchronous imaging system for human body security inspection according to claim 1, characterized in that the radiometer (3) is a direct detection type W-band millimeter wave radiometer, which is composed of a first LNA cascade unit (301), a second LNA cascade unit (302), a detector unit (303) and a video amplifier unit (304); the Cassegrain antenna feed source is connected with a first LNA cascade unit (301), the first LNA cascade unit (301) is connected with a second LNA cascade unit (302), the second LNA cascade unit (302) is connected with a detector unit (303), and the detector unit (303) is connected with a video amplifier unit (304).
3. The W-band passive millimeter wave dual-channel synchronous imaging system for human body security inspection according to claim 1, characterized in that: the system adopts a double-turntable spiral scanning mode to synchronously scan and image the double-channel targets at two sides of the system; the scanning control unit (11) controls the two servo motors to drive the horizontal rotary table (6) and the longitudinal rotary table (4) to simultaneously rotate at a constant speed according to a set rotating speed, so that the transverse and longitudinal scanning of a target scene to be detected is respectively realized; wherein, the maximum rotation angle of the horizontal turntable (6) is 45 degrees, and the rotation angle of the longitudinal turntable (4) is 360 degrees and rotates at a constant speed.
4. An imaging method using the imaging system of claim 1, wherein the smooth metal reflecting surface (1) rotates at a constant speed along the axis, two longitudinal sensor blocking pieces (704, 705) rotating together with the smooth metal reflecting surface sequentially pass through the longitudinal optical fiber sensor (502), and respectively control the data acquisition unit (9) to acquire data of target scenes of the left channel and the right channel of the system, the acquisition is stopped when the smooth metal reflecting surface (1) rotates away from the target scenes, and when the next longitudinal optical fiber sensor (502) generates a trigger pulse, the horizontal turntable (6) just rotates by an offset angle in the horizontal direction, and then the data acquisition of the next column is started until the data acquisition of the whole scene is completed; the collected data is processed by a corresponding algorithm to obtain a gray value or a pseudo-color value of a dual-channel target to be detected, and a millimeter wave image synchronously scanned by the two channels is displayed on the computer (10).
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| CN109581527B (en) * | 2018-12-21 | 2020-11-27 | 济南爱我本克网络科技有限公司 | Driving device and method for rotating mechanism of double-arm millimeter wave imaging system |
| CN109613619B (en) * | 2018-12-21 | 2020-11-17 | 济南爱我本克网络科技有限公司 | Driving device and method for rotating mechanism of single-arm millimeter wave imaging system |
| CN109725363B (en) * | 2019-01-18 | 2020-11-24 | 徐州纽卡电子科技有限公司 | Millimeter wave imaging double-side scanning detection system |
| CN110531436A (en) * | 2019-09-06 | 2019-12-03 | 哈尔滨工业大学 | A kind of two-dimensional scanning passive millimeter wave imaging system and method |
| CN111983606A (en) * | 2020-09-03 | 2020-11-24 | 安徽雷鼎电子科技有限公司 | Near-field imaging method of rolling type one-dimensional array radar |
| CN113009588B (en) * | 2021-03-01 | 2023-05-02 | 杭州睿影科技有限公司 | Human body security inspection equipment based on millimeter wave imaging |
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