CN104965233B - Multifrequency Terahertz detection system - Google Patents

Abstract

The invention discloses a kind of multifrequency Terahertz detection systems comprising: terahertz optics system is suitable for obtaining the background THz wave that the THz wave for being detected human body sending or object to be detected are reflected, and assembles to it；The detector of multiple and different frequencies, is suitable for receiving the THz wave for the different frequency that the terahertz optics system is assembled respectively, and the THz wave of respective frequencies is converted into electric signal respectively；Detected human body or object to be detected is imaged in imaging device, the electric signal and its imaging position for being suitable for being transmitted according to the detector；The display device is suitable for showing the imaging device imaging on a display screen.It can detecte dangerous goods entrained in the objects such as human body or luggage using multifrequency Terahertz detection system of the invention, and can classify to it.

Description

Multi-frequency terahertz detection system

Technical Field

The invention relates to the technical field of terahertz imaging, in particular to a multi-frequency terahertz detection system for detecting a human body, articles carried by the human body, luggage running on a conveyor belt and other objects.

Background

Terahertz (THz) waves refer to electromagnetic waves having a frequency range between 0.1 and 10THz (i.e., a wavelength of 3000 to 30) (1THz is 1012 Hz). The long wave band of the terahertz wave coincides with the millimeter wave (sub-millimeter wave), and the short wave band coincides with the infrared ray (far infrared ray), which belongs to the wave band which is less researched by the predecessor. Terahertz has many unique advantages, for example, the photon energy of terahertz wave is far lower than that of visible light and X-ray, and is only one thousandth of visible light, and one millionth of X-ray has little harm to human body, and does not produce harmful ionization effect on biological tissues. The terahertz wave is long in wavelength, the wavelength of the electromagnetic wave of 1THz is 300, and the influence of substance scattering is small when the terahertz wave is used for measurement and detection; in addition, terahertz waves have a very good penetrating power, for example, terahertz radiation can penetrate through substances such as fat, carbon plates, cloth, plastics, ceramics, fur, even most of non-metallic materials and non-polar substances with very little attenuation, and is absorbed or reflected by metals, colloids, explosives, drugs, currency, liquids and the like in a large amount. Therefore, the terahertz technology is used as a public security detection technology, and has great application requirements in occasions with dense people flows, such as airports, subways, railway stations and the like.

At present, the main passive imaging technique that is applied to terahertz imaging system through scanning the formation of image to human body or object fast, reaches the target that detects the hazardous articles etc. of placing in the hidden thing or the object (such as luggage etc.) that the human body carried, but can not classify the article that detect, and imaging speed and formation of image quality remain to be further improved.

Disclosure of Invention

In view of the above problems, the present invention has been made to provide a multi-frequency terahertz detection system that overcomes or at least partially solves the above problems.

According to the invention, a multi-frequency terahertz detection system is provided, which comprises a terahertz optical system, a plurality of detectors with different frequencies, an imaging device and a display device. The terahertz optical system acquires terahertz waves emitted by a detected human body and terahertz waves emitted by the detected human body after the terahertz waves are scattered, transmitted and/or absorbed by an article carried by the detected human body or background terahertz waves reflected by a detected object, and converges the terahertz waves; the detectors with different frequencies are selected according to the type of the detected object and the response of the detected object to different frequencies, are suitable for respectively receiving the terahertz waves with different frequencies converged by the terahertz optical system and respectively converting the terahertz waves with corresponding frequencies into electric signals; the imaging device images and fuses the detected human body or the detected object respectively according to the electric signals transmitted by the plurality of different detectors; the display device displays an image formed by the imaging device on a display screen. The terahertz optical system can comprise a scanning device and a focusing lens, wherein the scanning device is suitable for scanning a detected human body and an article carried by the detected human body or a detected object through rotation to obtain terahertz waves radiated by the detected human body and terahertz waves scattered, transmitted and/or absorbed by the article carried by the detected human body or background terahertz waves reflected by the detected object; the focusing lens is suitable for converging the terahertz waves acquired by the scanning device.

Optionally, the scanning means and the focusing means are realized by rotatable ellipsoidal mirrors, which combine the scanning and focusing functions.

Optionally, the plurality of detectors of different frequencies are a plurality of detectors of two or more frequencies. Optionally, the plurality of detectors are arranged in a rectangle. For example, when 3 frequencies of 12 detectors are used, 4 detectors for each frequency, the 12 detectors are arranged in a 3X4 array or a 4X3 array. Optionally, the plurality of detectors are arranged in a linear fashion. Optionally, the plurality of detectors are arranged in a plurality of rows with a fault. For example, when 12 detectors of three frequencies are used, 4 detectors of each frequency, the 12 detectors are arranged in three rows, and the middle row differs from the upper and lower rows by a distance of half the width of the detector.

By utilizing the multi-frequency terahertz detection system, dangerous articles carried by a human body or dangerous articles contained in objects such as luggage and the like can be detected and classified.

The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

fig. 1 shows a schematic diagram of a multi-frequency terahertz detection system according to an embodiment of the present invention;

fig. 2A and 2B illustrate images of a human body to be detected obtained by detection by the multi-frequency terahertz detection system of the present invention;

FIG. 3 shows a schematic view of one embodiment of the placement among a plurality of detectors according to the present invention;

FIG. 4 shows a schematic view of another embodiment of the placement of a plurality of detectors according to the present invention; and

fig. 5 shows a schematic view of a further embodiment of the arrangement of a plurality of detectors according to the invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

Fig. 1 shows a schematic diagram 100 of a multi-frequency terahertz detection system according to an embodiment of the invention. As shown in fig. 1, the multi-frequency terahertz detection system 100 includes: a terahertz optical system 110, a plurality of detectors 140 of different frequencies, an imaging device 150, and a display device 160. The terahertz optical system 110 acquires terahertz waves radiated by the human body 170 to be detected, terahertz waves scattered, transmitted and/or absorbed by an article carried by the human body to be detected, or background terahertz waves reflected by the object to be detected 170. The object carried by the detected human body is dangerous goods such as explosives, guns, knives and the like. The detected objects comprise luggage and the like containing dangerous goods such as explosives, guns, knives and the like. Generally, a human body radiates terahertz waves of various frequencies. There are also objects radiating terahertz waves of different frequencies around the object to be detected, and the object to be detected reflects terahertz waves radiated by other objects around the object to be detected. The terahertz optical system 110 acquires terahertz waves radiated by a detected human body, terahertz waves scattered, transmitted and/or absorbed by an article carried by the detected human body, or background terahertz waves reflected by a detected object, and transmits the terahertz waves to the detectors 140 with different frequencies, and the detectors 140 with different frequencies convert the terahertz waves with corresponding frequencies into electric signals and output the electric signals to the imaging device 150. The imaging device 150 images the human body 170 and the articles carried by the human body or the object 170 according to the electric signals transmitted by the different detectors, and then displays the images on the display device 160.

The terahertz optical system 110 may include a scanning device 120 and a focusing device 130. The scanning device 120 is adapted to scan the human body or object 170 to be detected, and can use two opposite, off-axis circular plane mirrors which can rotate to realize two-dimensional point-by-point scanning; and can also be realized by adopting a rotating mirror. The rotating mirror can adopt a rotatable regular polyhedron prism, namely, the cross section of the polyhedron prism is a regular polygon, the side surfaces of the regular polyhedron prism are plane reflecting surfaces, and when the rotating mirror rotates, terahertz waves received by the rotating mirror from a detected human body, terahertz waves scattered, transmitted and/or absorbed by an article carried by the detected human body, or background terahertz waves reflected by the detected object can be continuously reflected to the focusing device 130. For example, a regular pentahedron prism capable of rotating may be used, which can project the terahertz waves emitted from the human body onto the focusing device 130 by reflection of the planar reflection surface on the rotating mirror, and the rotating mirror can scan the human body for one circle, so as to continuously obtain the terahertz waves radiated by the human body to be detected, the terahertz waves scattered, transmitted and/or absorbed by the articles carried by the human body to be detected, or the background terahertz waves reflected by the object to be detected. The scanning device 120 starts to operate when the terahertz imaging system 100 of the present invention is powered on. The focusing device 130 is adapted to converge terahertz light obtained when the scanning device 120 scans the human body or the object to be detected, and then transmit the converged terahertz light to the detectors 140 with different frequencies, so as to facilitate the detection of the detectors 140, because the probes of the detectors 140 are relatively small, if the detection range is too large, the detection effect of the detectors 140 is affected. The focusing device 130 may be implemented using, for example, a convex lens.

In addition, the scanning device 120 and the focusing device 130 can also be implemented by using an ellipsoidal mirror, which combines the scanning and focusing functions.

The detector 140 includes a plurality of detectors with different frequencies, and may also be a detector with a plurality of probes, and the detection frequencies of different probes may be different. The detectors 140 with different frequencies or the probes with different frequencies of the detectors 140 respectively detect the terahertz waves with different frequencies radiated by the human body 170 to be detected, the terahertz waves scattered, transmitted and/or absorbed by the articles carried by the human body to be detected, or the background terahertz waves reflected by the object 170 to be detected with different frequencies. Optionally, the detectors 140 of the plurality of different frequencies are placed at or near the focal plane of the focusing device 130 in the terahertz optical system 110. The detector may be, for example, a pyroelectric detector that detects micro-thermal radiation.

The following description will mainly use the human body and the articles carried by the human body as an example to describe in detail how to use a plurality of detectors to detect the human body. The same applies to the detection of other objects, such as luggage on a conveyor belt, except that the terahertz waves detected at this time come from the reflection of terahertz waves radiated by the object, such as the luggage, on its surroundings.

Because the detected human body can radiate the terahertz waves with different frequencies, when the detected human body carries different articles, the terahertz waves with different frequencies are transmitted, scattered and/or absorbed by the different articles carried by the human body, the intensity changes of the terahertz waves are different, and after the detectors with different frequencies detect the terahertz waves with different intensity changes, different electric signals can be generated, so that the transmission, scattering and/or absorption characteristics of the terahertz waves by the different articles can be reflected. The imaging device 150 performs imaging based on different electrical signals, and the image of the region of the detected human body carrying these different objects is compared with the background image around these objects, so that the features and kinds of these objects can be identified.

For example, when three detectors with different detection frequencies are used for detection, the detection frequencies adopted by the three detectors are, for example, 360GHz, 220GHz and 94GHz, respectively, and when an explosive, a cutter, a pistol and other objects are carried on the detected human body 170, the objects such as the explosive, the cutter, the pistol and the like have different transmission, scattering and/or absorption characteristics for the terahertz waves radiated by the human body, so that the objects such as the explosive, the cutter, the pistol and the like have different transmittances for the terahertz waves with different frequencies radiated by the human body parts at the positions of the objects, and the intensity of the terahertz waves radiated by the human body parts is changed. The detectors of different detection frequencies detect terahertz waves of different frequencies and convert them into electrical signals, such as voltage signals, which vary linearly with the intensity of the terahertz waves radiated from different parts of the human body to be detected. For example, due to the difference in the transmission, scattering, and/or absorption characteristics of different explosives on terahertz waves of different frequencies, terahertz waves radiated from a human body part carrying explosives are detected by detectors of 360GHz, 220GHz, and 94GHz to obtain signals of voltage A, B, C, where a is not equal to B not equal to C. Terahertz waves radiated by human body parts carrying articles such as metal cutters, handguns and the like are detected by detectors of 360GHz, 220GHz and 94GHz to respectively obtain signals of voltage D, D, D. The voltage A, B, C, D is smaller than a voltage obtained by detecting a terahertz wave radiated from a human body part where an explosive, a knife, a pistol, or the like is not placed. Therefore, when the imaging device 150 performs imaging based on the electrical signal generated by the detector 140 of the same frequency and the imaging position thereof (determined based on the position of the detected human body or object corresponding to the terahertz wave converged by the terahertz optical system 110), images with different contrast and different depths are formed at different parts of the human body, and then images with different colors formed by the detectors of different frequencies (for example, when the detectors of three frequencies are used for detection, images with 3 different colors are formed) are fused, so that the image recognition effect can be further improved. Fig. 2A shows an image of the front of the detected human body, and as shown in fig. 2A, there are four black images of the chest, abdomen, and right side of the detected human body, which shows that articles are placed on all four parts of the detected human body. Fig. 2B shows an image of the back of the detected person, and as shown in fig. 2B, the right hip shows a black image shaped like a pistol. In practice, the imaging device 150 can mark different colors on the images according to the difference of the electrical signals generated by the detectors with different detection frequencies and the shapes of the electrical signals when the electrical signals are imaged, so that the inspector can quickly identify what the object is.

The multi-frequency terahertz detection system can detect different articles carried by a detected human body more sensitively, and as long as different articles are carried, the terahertz waves radiated by the human body can be transmitted, scattered and/or absorbed to different degrees, namely, the terahertz waves are attenuated to different degrees, so that finally the formed human body image can generate shades with different depths and different shapes or be marked with different colors at different parts of the human body, thereby reminding detection personnel to pay attention.

In addition, some articles have a high transmittance for terahertz waves of a certain frequency, and when such articles are hidden in the body of the subject, if a detector of such a frequency is used for detection, such articles are hardly detected. However, the transmittance of the article to the terahertz waves of other frequencies may not be too high, that is, the article has relatively large absorption and/or scattering to the other frequencies, so that when the detector of the other frequencies is used for detection, the attenuation of the terahertz waves of the frequency can be detected, and the object carried on the detected human body can be detected. For example, if a nail object absorbs terahertz waves strongly at 220GHz, but absorbs them weakly at 360 GHz. The object B absorbs the terahertz waves with the frequency of 220GHz weakly, but absorbs the terahertz waves with the frequency of 360GHz strongly. Thus, the presence of the object A can be detected by the detector at 220GHz, and the detection of the object B is ambiguous; the presence of the second object can be detected by a 360GHz detector, and the detection of the first object is ambiguous. Therefore, the multi-frequency terahertz detection system can improve the detection rate of suspicious articles carried by detected people and prevent detection omission. On one hand, the human body is damaged, and on the other hand, some articles do not have the blocking effect or have the very weak blocking effect on the X rays, for example, some polymers and foam materials do not form images after the X rays are detected, so that the problem of missed detection can be caused. However, with the multi-frequency terahertz detection system of the present invention, such a problem is avoided.

The number of detectors with different frequencies is determined according to the requirement, and the number of detectors with different frequencies is generally the same, so that the subsequent image processing is easier. In addition, the detector with two different detection frequencies can be adopted for detection, the detector with more than three different detection frequencies can be adopted for detection, and the detection frequency can be determined according to the types of the detected articles and the responses of the detected articles to the different frequencies. Likewise, an array detector having a plurality of probes with different probing frequencies may also be employed.

When a plurality of detectors 140 with different frequencies are used, the arrangement of the detectors 140 affects the imaging speed, and affects the subsequent image processing of the imaging device 150. When the multi-frequency terahertz detection system is closer to the detected human body or object, the detector is closer to the detected human body or object, so that the detected terahertz wave signal is stronger, the corresponding electric signal formed by the detector is stronger, and the contrast of the image formed by the imaging device is higher. In addition, as more detectors 140 are used, the spatial region areas detected by these detectors become larger each time the terahertz optical system 110 scans, the time required for scanning imaging decreases for a certain imaging area range, and the imaging speed becomes faster.

FIG. 3 is a schematic diagram of one embodiment of the placement of multiple detectors. As shown in FIG. 3, when 12 detectors are used, the first row positions 4 detectors at 94GHz along the line, the second row positions 4 detectors at 220GHz along the line, and the third row positions 4 detectors at 360GHz, forming a 3X4 array. The placing mode is simple, and the processing and the system integration are easy. As described above, since the method shown in fig. 3 uses many detectors, the imaging speed is increased.

In addition, the 12 detectors are not limited to the above-mentioned arrangement, for example, at least one detector with different frequency is arranged in each row. Also, the 12 detectors can be arranged in a 4 × 3 array, and so on. In a word, a better placing mode can be selected according to the situation.

When the placement mode shown in fig. 3 is adopted for the plurality of detectors, the rotating mirror described above can be used as the scanning device 120, so that the 12 detectors can receive corresponding terahertz waves at the same time when the rotating mirror rotates each time.

Fig. 4 shows a schematic view of another embodiment of the arrangement of a plurality of detectors. As shown in FIG. 4, the three detectors are arranged in a straight line shape from top to bottom, and the frequencies of the three detectors are 94GHz, 220GHz and 360GHz respectively from top to bottom. The arrangement mode only adopts three detectors, the number is small, the cost is low, and the imaging speed is slower compared with the mode of figure 4.

In addition, the three detectors in fig. 4 may also be placed in a straight line shape from left to right, and the positions of the detectors with different frequencies are not limited to the detectors with 94GHz, 220GHz, and 360GHz from left to right, which is not limited by the present invention.

When the placement mode shown in fig. 4 is adopted for the plurality of detectors, the two opposite off-axis circular plane mirrors capable of rotating as described above can be adopted as the scanning device 120 to realize two-dimensional point-by-point scanning, and the 3 detectors can receive corresponding terahertz waves at the same time through the high-speed rotation of the circular plane mirrors.

Fig. 5 shows a schematic view of a further embodiment of the arrangement of a plurality of detectors. As shown in FIG. 5, the 12 detectors 140 are arranged in three rows in the manner shown in FIG. 5, each row containing 4 detectors. Wherein the detectors of the first row differ from the detectors of the second row by half the width of a detector (when a single pixel detector is used, the detectors of two adjacent rows differ by half a pixel), and the detectors of the second row differ from the detectors of the third row by half the width of a detector. The mode shown in fig. 5 uses more detectors and has high imaging speed. Because the width of the half detector is staggered between two adjacent lines, the actually generated electric signals are also staggered in the distribution of the corresponding imaged pixel points, so that the imaging device 150 can interpolate on the basis of the actual pixels to generate more pixels when performing image processing, and the imaging resolution can be improved, and the arrangement mode shown in fig. 5 enables the imaging resolution of the imaging device 150 to be improved greatly compared with the arrangement mode shown in fig. 3. Fig. 5 shows only one arrangement in which two adjacent rows of detectors are offset from each other, but other similar arrangements are possible, for example, in fig. 5 the third row is offset to the right by half the width of the detectors from the second row, so that the third row is offset from the first row by the width of one detector. The present invention is not particularly limited in this regard. The offset distance may be adjusted as necessary.

The placement of the plurality of detectors shown in fig. 5 is similar to the placement shown in fig. 3, and the scanning device 120 may also employ a turning mirror as described above.

The above description only shows several embodiments of the placement modes of the plurality of detectors, and the present invention is not limited to the above placement modes, and more or fewer detectors with different frequencies may be used according to the needs, and the corresponding scanning device and focusing device may be adjusted accordingly to obtain better effects.

The imaging device 150 may be a computer, a single chip, or a microprocessor, and is configured to image the detected human body, the carried object, or the detected object according to the electrical signal generated by the detector and the imaging position thereof.

The display device 160, which is connected to the imaging device 150, may be a computer screen or other device for displaying images formed by the imaging device 150.

The multi-frequency terahertz detection system can detect the detected human body and the forbidden articles carried by the detected human body and the forbidden articles contained in objects such as concealed forbidden articles and luggage through the detectors with multiple frequencies, so that a detection person can easily obtain the specific position of the suspicious article carried by the detected human body and whether the detected object contains the forbidden articles, and can detect by the detectors with different frequencies according to the different transmittances of different articles on terahertz waves radiated by the human body at different frequencies and the different degrees of reflection of the objects contained in the objects such as luggage on the terahertz waves radiated around to obtain different electric signals, and can quickly identify different articles based on different colors and the shapes of the formed images by imaging and processing based on the electric signals and the imaging positions thereof if different colors are marked again, therefore, the aim of quickly identifying hidden dangerous articles carried by human bodies or luggage, such as explosives, cutters, handguns and the like, is fulfilled. In addition, the multi-frequency terahertz detection system has the advantages of high imaging speed, strong recognition capability and high imaging quality.

In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Those skilled in the art will appreciate that the modules in the device in an embodiment may be adaptively changed and disposed in one or more devices different from the embodiment. The modules or units or components of the embodiments may be combined into one module or unit or component, and furthermore they may be divided into a plurality of sub-modules or sub-units or sub-components. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes or elements are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.

The various component embodiments of the invention may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that a microprocessor or Digital Signal Processor (DSP) may be used in practice to implement some or all of the functionality of some or all of the components in a browser client according to embodiments of the present invention. The present invention may also be embodied as apparatus or device programs (e.g., computer programs and computer program products) for performing a portion or all of the methods described herein. Such programs implementing the present invention may be stored on computer-readable media or may be in the form of one or more signals. Such a signal may be downloaded from an internet website or provided on a carrier signal or in any other form.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.

Claims (7)

1. Multi-frequency terahertz detection system, characterized in that the system includes:

the terahertz optical system is suitable for acquiring terahertz waves emitted by a detected human body, terahertz waves emitted by the detected human body after the terahertz waves are scattered, transmitted and/or absorbed by an article carried by the detected human body, or background terahertz waves reflected by a detected object, and converging the terahertz waves;

a plurality of detectors of different frequencies selected according to the kind of the object to be detected and their responses to the different frequencies, the plurality of detectors of different frequencies being adapted to receive terahertz waves of different frequencies condensed by the terahertz optical system, respectively, and convert the terahertz waves of corresponding frequencies into electrical signals, respectively;

the imaging device is suitable for respectively imaging and fusing the detected human body or the detected object according to the electric signals transmitted by the plurality of different detectors and the imaging positions of the electric signals; and

a display device adapted to display an image formed by the imaging device on a display screen; wherein,

the terahertz optical system comprises a scanning device and a focusing device, wherein,

the scanning device is suitable for scanning a detected human body and an article carried by the detected human body or an object to be detected through rotation to obtain terahertz waves radiated by the detected human body, terahertz waves scattered, transmitted and/or absorbed by the article carried by the detected human body or background terahertz waves reflected by the detected object;

the focusing device is suitable for converging the terahertz waves acquired by the scanning device.

2. The multi-frequency terahertz detection system of claim 1,

the scanning device and the focusing device are realized by an ellipsoidal reflector which can rotate and combine the scanning function and the focusing function into a whole.

3. The multi-frequency terahertz detection system of claim 1,

the plurality of detectors are arranged in a rectangle.

4. The multi-frequency terahertz detection system of claim 1,

when 3 frequencies of 12 detectors are used, 4 detectors for each frequency, the 12 detectors are arranged in a 3X4 array or a 4X3 array.

5. The multi-frequency terahertz detection system of claim 1,

the plurality of detectors are arranged in a linear fashion.

6. The multi-frequency terahertz detection system of claim 1,

the plurality of detectors are arranged in a plurality of rows in a staggered manner.

7. The multi-frequency terahertz detection system of claim 6,

when 12 detectors of three frequencies are used, 4 detectors of each frequency, the 12 detectors are arranged in three rows, and the middle row differs from the upper and lower rows by a distance of half the width of the detector.