CN209784559U - Millimeter wave terahertz imaging device - Google Patents
Millimeter wave terahertz imaging device Download PDFInfo
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- CN209784559U CN209784559U CN201822275909.4U CN201822275909U CN209784559U CN 209784559 U CN209784559 U CN 209784559U CN 201822275909 U CN201822275909 U CN 201822275909U CN 209784559 U CN209784559 U CN 209784559U
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Abstract
A millimeter wave terahertz imaging apparatus for performing security inspection on an object to be inspected, comprising a focusing lens, a detector and a pattern processing device, wherein the focusing lens is disposed between the object to be inspected and the detector and is configured to focus a millimeter wave terahertz wave spontaneously radiated or reflected by the object to be inspected on the detector; a detector including an antenna array and a detector array, wherein the antenna array is disposed on a side of the detector array facing the focusing lens and is disposed as an antenna port of the detector array, and the detector array is disposed on a focal plane of the focusing lens and is configured to convert millimeter wave terahertz waves received by the antenna array into a polarized image of a detected object; and the image processing device is arranged on one side of the detector array far away from the antenna array and is configured to process the polarization image to identify and classify the detected object.
Description
Technical Field
The utility model relates to a security check technical field especially relates to a millimeter wave terahertz imaging device.
Background
The existing passive millimeter wave terahertz imaging is similar to optical shooting, one two-dimensional array surface (a detector (or a radiometer, or a detector, or direct detection or indirect detection) of each array element corresponds to one pixel, and the array elements in an array form one array surface) is utilized to stare a target field of view, so that scanning is not needed, and real-time imaging can be realized.
Considering the cost of the millimeter wave terahertz detector, completely adopting a two-dimensional focal plane direct imaging mode leads to very high cost of the whole system. Therefore, in order to meet the requirements of system cost and imaging rate in practical application, for two-dimensional imaging, the current mainstream system adopts a mode of a certain number of radiometers and mechanical scanning to realize scanning coverage of the whole field of view, and the requirement for few detectors is reduced by sacrificing imaging time, so that the cost of the whole system is reduced.
The existing passive millimeter wave terahertz imaging security inspection device based on focal plane imaging can only display the image shape of a suspicious object (such as a mobile phone, a bank note, a cutter, a pistol and the like) through the temperature difference between the suspicious object and a human body no matter the traditional passive millimeter wave terahertz imaging security inspection device adopts direct detection of a radiometer or indirect detection of a heterodyne method, so that whether the human body carries the suspicious object or not is determined, and object identification cannot be carried out on the suspicious object. Usually, the temperature of the body surface of the human body is higher than that of the suspicious object, and the human body is displayed to be white on the imaging gray image, and the suspicious object is black. In general, belt buckles, cellular phones, metal blocks, media blocks, paper money, and the like having similar shapes and sizes cannot be subject to object recognition regardless of machine recognition or manual recognition.
In addition, the resolution (object direction) of the passive human body security inspection device is only 2-3cm, which is not good for object classification and identification by size and shape.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to solve at least one aspect among the above-mentioned technical problem, provide a millimeter wave terahertz imaging device and utilize object identification and classification method that this equipment goes on. Through this millimeter wave terahertz imaging equipment can be on the basis of not producing harmful radiation to the human body, discerned the object in order to classify the object, and the size of the object of discerning can reach millimeter level's structure.
In one aspect according to the present invention, there is provided a millimeter wave terahertz imaging apparatus for performing a security inspection on an object to be inspected, comprising a focusing lens, a detector and a pattern processing device, wherein the focusing lens is disposed between the object to be inspected and the detector, and is configured to focus a millimeter wave terahertz wave which is spontaneously radiated or reflected by the object to be inspected on the detector; a detector including an antenna array and a detector array, wherein the antenna array is disposed on a side of the detector array facing the focusing lens and is disposed as an antenna port of the detector array, and the detector array is disposed on a focal plane of the focusing lens and is configured to convert millimeter wave terahertz waves received by the antenna array into a polarized image of a detected object; and the image processing device is arranged on one side of the detector array far away from the antenna array and is configured to process the polarization image to identify and classify the detected object.
according to an exemplary embodiment of the present invention, the antenna array comprises a plurality of receiving antennas, each of the plurality of receiving antennas being linearly polarized or circularly polarized.
According to another exemplary embodiment of the present invention, the detector array includes a plurality of wave sensing units, the number of the plurality of wave sensing units is the same as the number of the plurality of receiving antennas, and the position of each wave sensing unit on the detector array corresponds to the position of each receiving antenna on the antenna array.
According to another exemplary embodiment of the present invention, the antenna array is a one-dimensional array, the detector array is a one-dimensional array, the one-dimensional antenna array comprises a plurality of macro-pixel units arranged linearly, wherein each macro-pixel unit is an antenna array of N × 1, wherein N is a positive integer, and N is greater than or equal to 3, and each macro-pixel unit comprises at least N-1 different polarization angles.
According to another exemplary embodiment of the present invention, the antenna array is a two-dimensional array, the detector array is a two-dimensional array, the two-dimensional antenna array comprises a plurality of macro-pixel units arranged on a two-dimensional plane, wherein each macro-pixel unit is M1*M2Of antenna array, wherein M1，M2Is a positive integer, and M1，M2≧ 2, and each macropixel unit includes at least N-1 different polarization angles, where N ═ M1*M2。
According to another exemplary embodiment of the present invention, the N receiving antennas of each macro-pixel unit comprise at least one of the following: n linearly polarized receiving antennas; n-1 linear polarization receiving antennas and a circular polarization receiving antenna.
According to another exemplary embodiment of the present invention, the polarization angles of the N linearly polarized receiving antennas are Deg1, Deg2, Deg3, … DegN, respectively, wherein
Wherein i is a positive integer less than or equal to N.
According to another exemplary embodiment of the present invention, the polarization angles of the N-1 linearly polarized receiving antennas are Deg1, Deg2, Deg3, … DegN-1, respectively, wherein
Or
Wherein i is a positive integer less than or equal to N-1;
Wherein the circular polarization includes at least one of left-hand circular polarization and right-hand circular polarization.
According to the utility model discloses a millimeter wave terahertz imaging device still includes millimeter wave terahertz radiation source, and it is used for radiating millimeter wave terahertz wave to the examined object.
According to another exemplary embodiment of the present invention, the antenna array is a one-dimensional array, the detector array is a one-dimensional array, and the millimeter wave terahertz imaging apparatus further includes a rotatable scanning mirror disposed in a light path between the inspected object and the focusing lens.
According to another exemplary embodiment of the present invention, the rotatable scanning mirror is rotatable to image a specific portion on the object to be inspected on a specific wave sensing unit of the one-dimensional detector array at one specific rotation angle.
According to the utility model discloses an among the millimeter wave terahertz imaging device, through setting up one-dimensional or two-dimensional antenna array, can obtain the polarization image of examining the object. After the polarization image is processed by the image processing device, a high-resolution image with polarization information can be obtained. The polarization imaging technology can detect structural information of the surface of an object, such as roughness and texture, and can also detect information of conductivity, refractive index and the like of the surface of the object, and the scheme provides more information than the existing passive terahertz imager (only can detect the strength information of the surface of the object), and the information is very useful for object classification and object identification. By means of the acquired polarization information, such as different surface textures, roughness, refractive index, conductivity and the like of the material, suspicious objects with similar shapes and sizes can be distinguished, namely identified and classified. Furthermore, according to the utility model discloses an object size that millimeter wave terahertz imaging equipment can discern can reduce to the millimeter rank.
drawings
Fig. 1 shows a passive millimeter wave terahertz imaging device according to an embodiment of the present invention.
Fig. 2 shows an active millimeter wave terahertz imaging device according to an embodiment of the present invention.
Fig. 3 shows an imaging schematic diagram of a millimeter wave terahertz imaging device including a two-dimensional antenna array according to an embodiment of the present invention.
Fig. 4 shows an imaging schematic diagram of a millimeter wave terahertz imaging device including a one-dimensional antenna array according to an embodiment of the present invention.
Fig. 5A and 5B show simplified schematic diagrams of a macro-pixel cell of a two-dimensional antenna array according to an embodiment of the invention.
Fig. 6A and 6B show simplified schematic diagrams of a macro-pixel cell of a two-dimensional antenna array according to an embodiment of the invention.
Fig. 7 shows a simplified schematic diagram of a macro-pixel cell of a one-dimensional antenna array according to an embodiment of the invention.
Fig. 8 shows a simplified schematic diagram of a macro-pixel cell of a one-dimensional antenna array according to an embodiment of the invention.
Fig. 9 shows an image obtained by a detector array according to an embodiment of the invention.
Fig. 10 shows 4 low resolution polarization images extracted from an image obtained from a detector array according to an embodiment of the invention.
Detailed Description
While the present disclosure will be fully described with reference to the accompanying drawings, which contain preferred embodiments of the disclosure, it should be understood before this description that one of ordinary skill in the art can modify the disclosure described herein while obtaining the technical effects of the present disclosure. Therefore, it should be understood that the foregoing description is a broad disclosure directed to persons of ordinary skill in the art, and that there is no intent to limit the exemplary embodiments described in this disclosure.
Furthermore, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in schematic form in order to simplify the drawing.
Fig. 1 shows passive millimeter wave terahertz imaging equipment according to the utility model discloses. As shown in fig. 1, the millimeter wave terahertz imaging apparatus for performing security inspection on an object 1 to be inspected includes a focusing lens 3, a detector 4, and a pattern processing device 6. The focusing lens 3 is between the object 1 and the detector 4, and is configured to focus the millimeter wave terahertz waves 2, which are spontaneously radiated or reflected by the object, on the detector 4. The detector comprises an antenna array 41 and a detector array 42 (shown in fig. 3 and 4), wherein the antenna array 41 is arranged on one side of the detector array 42 facing the focusing lens 3 and is arranged as an antenna port of the detector array 42, and the detector array 42 is arranged on a focal plane of the focusing lens 3 and is configured to convert millimeter wave terahertz waves received by the antenna array into a polarized image of the detected object 1. The image processing device 6 is disposed on a side of the detector array 42 away from the antenna array 41, and is configured to process the polarization image to perform identification classification on the detected object.
Detectors of typical millimeter wave terahertz imaging devices are all provided with antenna ports, and the main purpose of the antenna ports is to increase received power and improve receiving efficiency. In the present invention, the antenna array 41 is provided as an antenna port of the detector and communicates with the detector array 42, so that the detector itself has a function of selecting a polarization direction.
In one embodiment according to the present invention, the image processing apparatus 6 includes an analog signal processor 61, a digital-to-analog converter (D/a converter) 62, a digital signal processor 63, and an image display 64. The detector array 42 converts the incident millimeter wave terahertz waves into electric signals on each pixel point, and sends the electric signals to the analog signal processor 61; the analog signal processor 61 is used for receiving the analog signal transmitted by the detector and transmitting the analog signal to the digital-to-analog converter 62; the digital-to-analog converter 62 is used for receiving the signal transmitted by the analog signal processor, performing digital-to-analog conversion on the signal and sending the signal to the digital signal processor 63; the digital signal processor 63 is configured to receive the information converted by the converter, perform a demosaicing process on the information, and display an image obtained by the demosaicing process on the image display 64, wherein a method of the demosaicing process will be described in detail below.
The utility model discloses in, terahertz wave is the electromagnetic wave that the frequency is in 100GHz to 10THz (10000GHz) scope does, and terahertz wave is between microwave and visible light, and at long wave band and millimeter wave coincidence, at short wave band and infrared ray coincidence. The frequency channel of millimeter wave is 26.5 to 300GHz, millimeter wave terahertz wave be the frequency channel and be located the electromagnetic wave between 30GHz to 1000 GHz. In the technical field of millimeter wave terahertz imaging apparatuses, since the energy of millimeter wave terahertz waves radiated or reflected by a human body is very low, it is appropriate for the millimeter wave terahertz waves to be used for security inspection.
Fig. 2 shows according to the utility model discloses an active millimeter wave terahertz imaging device. As shown in fig. 2, the active millimeter wave terahertz imaging apparatus further includes a millimeter wave terahertz radiation source 5 for radiating a millimeter wave terahertz wave to the object 1 to be inspected so that the object 1 to be inspected reflects the millimeter wave terahertz wave toward the focusing lens 3.
In one embodiment according to the present invention, the antenna array 41 includes a plurality of receiving antennas, each of which is linearly polarized or circularly polarized.
The type, structure and placement of the antenna determine the polarization (direction of polarization) of the antenna. Antennas commonly found in the art include horn antennas, patch antennas, helical antennas, and the like. The polarization angle of the horn antenna can be changed by arranging the horn antenna and the patch antenna in the arrangement direction relative to the horizontal direction. In a word, different linear polarization directions can be realized by different non-horizontal placing modes of the horn antenna, the patch antenna and the like. The horn antenna may have a rectangular or circular waveguide port. By setting the waveguide port to a circular waveguide port, the polarization mode of the horn antenna can be converted to circular polarization. In addition, the circular polarization of a horn antenna and the like can be realized by adding a dielectric wave plate into the rectangular waveguide port. In a word, the horn antenna and the patch antenna can realize circular polarization by adding a dielectric wave plate or structural design. The utility model discloses in, the size on each limit of horn antenna's waveguide mouth is preferably 0.1mm to 10mm to adapt to the not sensing wave unit of equidimension millimeter wave terahertz wave detector.
In an embodiment according to the present invention, the detector array 42 includes a plurality of wave-sensing units, the number of the wave-sensing units is the same as the number of the receiving antennas, and the position of each wave-sensing unit on the detector array corresponds to the position of each receiving antenna on the antenna array. In the millimeter wave terahertz imaging device according to the present invention, the pixel pitch of the antenna array is matched with the pixel pitch of the detector array; the crosstalk between adjacent wave sensing units of the detector array (mixed polarization information between adjacent pixels) is as small as possible.
in an embodiment according to the present invention, the antenna array may be a two-dimensional array or a one-dimensional array.
In an embodiment according to the present invention, when the antenna array is a two-dimensional array, the two-dimensional antenna array 41 includes a plurality of macro-pixel units arranged on a two-dimensional plane, where each macro-pixel unit is M1*M2Of antenna array, wherein M1，M2Is a positive integer, and M1，M2≧ 2, and each macropixel unit includes at least N-1 different polarization angles, where N ═ M1*M2
. In a specific embodiment, M is equal to 2, and each macro-pixel element is a 2 x 2 antenna array.
In an embodiment according to the present invention, when the antenna array is a one-dimensional array, the one-dimensional antenna array 41 includes a plurality of macro-pixel units arranged linearly, wherein each macro-pixel unit is an antenna array of N × 1, wherein N is a positive integer, and N is greater than or equal to 3, and each macro-pixel unit includes at least N-1 different polarization angles. In one specific embodiment, N is equal to 3, and one macro-pixel element is 3 x 1 of the antenna array.
The utility model discloses an among the millimeter wave terahertz imaging device, according to the size and the polarization direction of required macro-pixel unit, select different antenna kind, antenna structure and different antenna placing method.
In a specific embodiment according to the present invention, a terahertz wave detector with a center frequency of 94GHz is used, wherein the antenna array size is 120 × 160, the size of the horn mouth of the horn antenna is (rectangular waveguide mouth) 5.5mm × 4cm, and the detector array resolution is 120 × 160, and the pixel size is 5mm × 5 mm.
Fig. 3 shows an imaging schematic diagram of a millimeter wave terahertz imaging device including a two-dimensional antenna array according to an embodiment of the present invention. Fig. 4 shows an imaging schematic diagram of a millimeter wave terahertz imaging device including a one-dimensional antenna array according to an embodiment of the present invention.
In an embodiment according to the present invention, as shown in fig. 3, the antenna array is a two-dimensional antenna array, and the detector array is a two-dimensional detector array, in this schematic diagram, in order to show the schematic structure of the antenna array and the detector array more clearly, the antenna array and the detector array are separated by a certain distance, however, in the actual structure, each antenna is used as an antenna port of each sensing unit. So that the two-dimensional antenna array acts as an antenna port for the detector array. For example, in the case where the object to be detected is a person, millimeter wave terahertz waves from the head of the person are imaged on one or more first wave sensing units of a two-dimensional detector array after passing through a focusing lens and being received by a two-dimensional antenna array. Meanwhile, millimeter wave terahertz waves from the chest of the person are imaged on one or more second wave sensing units of the two-dimensional detector array after passing through the lens and being received by the two-dimensional antenna array, and the second wave sensing units are different in position from the first wave sensing units. Therefore, millimeter wave terahertz waves from a plurality of different positions can be detected and imaged at the same time throughout the two-dimensional detector array. When a suspicious object is detected, millimeter wave terahertz waves radiated or reflected from a plurality of positions on the suspicious object can be imaged.
In an embodiment according to the present invention, as shown in fig. 4, the antenna array is a one-dimensional antenna array, and the detector array is a one-dimensional detector array. The one-dimensional antenna array serves as an antenna port of the detector array. In this case, the millimeter wave terahertz imaging apparatus further includes a rotatable scanning mirror 7 disposed in the optical path between the object 1 to be inspected and the focusing lens 3. The rotatable scanning mirror 7 is rotatable to image a specific portion on the object to be examined on a specific wave sensing unit of the one-dimensional detector array at a specific rotation angle. For example, the millimeter wave terahertz imaging apparatus images the head of the subject on the first wave sensing unit of the one-dimensional detector array while the rotatable scanning mirror 7 is at the first rotation angle. When the rotatable scanning mirror 7 is at a second rotation angle different from the first rotation angle, the millimeter wave terahertz imaging device images the chest and other parts of the person to be examined on a second wave sensing unit of the one-dimensional detector array, which is different from the first wave sensing unit. The rotatable scanning mirror 7 is repeatedly rotated until the whole scanning of the object to be inspected is achieved, and each part is imaged on the one-dimensional detector array. By providing the rotatable scanning mirror 7, the number of expensive detector units can be reduced, thereby saving costs.
Identification and classification of the inspected objects is a major goal of millimeter wave detection research. The electromagnetic wave radiated from the object has polarization characteristics, and therefore more information on the object can be acquired by polarization information in the object radiation signal. The utility model provides a through the polarization degree that antenna kind or antenna placing mode controlled different detectors, that is to say in a macro pixel unit of antenna array or detector array, different ripples unit reception of feeling ripples is different polarization state's ripples. The split focal plane polarization imaging technology can be added with a receiving antenna array infinitely, and the structure is simple.
Utilize according to the utility model discloses an advantage of millimeter wave terahertz imaging device mainly embodies two aspects as follows.
In a first aspect, object classification and object identification may be performed using polarization information of a detected polarization image. This is because the polarization imaging technology can not only detect the structural information of the object surface, such as roughness and texture, but also detect the conductivity, refractive index, etc. information of the object surface, and this scheme provides more information than the existing passive terahertz imager (which can only detect the intensity information of the object surface), and these information are very useful for object classification and object identification. For example, a common passive millimeter wave terahertz security check instrument is adopted to detect suspicious objects carried by a human body, such as mobile phones, bank notes, cutters, handguns and the like, because the body surface temperature of the human body is higher than that of the suspicious objects, the human body is displayed to be white on an imaging gray image, and the suspicious objects are all black blocks. In general, belt buckles, cell phones, metal blocks, media blocks, and paper money of similar shapes and sizes cannot be distinguished whether they are machine identification or manual identification. We cannot distinguish the suspicious object by the shape of the black block. The obtained polarization information (different surface textures, roughness, refractive index, conductivity and the like of the material) is used for distinguishing suspicious objects with similar shapes and sizes by utilizing a polarization imaging technology.
On the other hand, super-resolution imaging can be realized through a super-resolution polarization imaging reconstruction algorithm, the resolution is improved by at least 4 times compared with the existing imaging image mode (polarization information cannot be obtained), the resolution can reach the millimeter level, and the method is very effective for identifying suspicious objects with millimeter-level structures.
The polarization of the one-dimensional antenna array and the two-dimensional antenna array will be described in detail below.
Fig. 5A and 5B show simplified schematic diagrams of a macro-pixel cell of a two-dimensional antenna array according to an embodiment of the invention. In this embodiment, the macropixel unit includes N linearized receive antennas having polarization angles of Deg1, Deg2, Deg3, … DegN, respectivelyi is a positive integer less than or equal to N. As shown in fig. 5A, when the number N of receiving antennas per macro-pixel unit is 4, the macro-pixel arrangement of one macro-pixel unit is linear polarization of 0 °, 45 °, 90 °, and-45 °. As shown in fig. 5B, one macro-pixel unit macro-pixel arrangement is linear polarization of 30 °, 75 °, 120 °, and-15 °.
Fig. 6A and 6B show simplified schematic diagrams of a macro-pixel cell of a two-dimensional antenna array according to an embodiment of the invention. In this embodiment, the macropixel cell comprises N-1 linearly polarized receiving antennas and 1 circularly polarized receiving antenna, the circular polarization may be either left-hand circular polarization or right-hand circular polarization, and the N-1 linear polarization angles are Deg1, Deg2, Deg3 and … Deg (N-1), respectively, whereinOri is a positive integer less than or equal to N-1. As shown in fig. 6A, when the number N of receiving antennas of each macro-pixel unit is 4, the polarization angles of the 4 receiving antennas are 0 ° linear polarization, 60 ° linear polarization, 120 ° linear polarization, and circular polarization. As shown in fig. 6B, when the number N of receiving antennas of each macro-pixel unit is 4, the polarization angles of the 4 receiving antennas are 0 ° linear polarization, 45 ° linear polarization, 90 ° linear polarization, and circular polarization.
Fig. 7 shows a simplified schematic diagram of a macro-pixel cell of a one-dimensional antenna array according to an embodiment of the invention. In this embodiment, the macropixel unit includes N linearly polarized receive antennas with polarization angles of Deg1, Deg2, Deg3, … DegN, respectively, whereIn one embodiment, as shown in fig. 7, when the number N of receiving antennas of one macropixel unit is 3, the macropixel arrangement of one macropixel unit is linear polarization of 0 °, 60 °, and 120 °.
Fig. 8 shows a simplified schematic diagram of a macro-pixel cell of a one-dimensional antenna array according to an embodiment of the invention. In this embodiment, the macropixel cell comprises N-1 linearly polarized receiving antennas and 1 circularly polarized receiving antenna, the circular polarization may be either left-hand circular polarization or right-hand circular polarization, and the N-1 linear polarization angles are Deg1, Deg2, Deg3 and … Deg (N-1), respectively, whereinIn one embodiment, as shown in fig. 8, when the number N of receiving antennas of one macro-pixel unit is 3, the macro-pixel arrangement of one macro-pixel unit is 0 ° linear polarization, 90 ° linear polarization, and circular polarization.
According to the millimeter wave terahertz imaging device, a method for identifying and classifying objects by using the millimeter wave terahertz imaging device can be realized. The method comprises the following steps: through the focusing lens, millimeter wave terahertz waves which are spontaneously radiated or reflected by the detected object are received by the antenna array and focused on the detector array; converting, by the detector array, the millimeter wave terahertz waves received by the antenna array into a polarization image (e.g., a polarization image as shown in fig. 9) of the object to be detected; processing the polarization image with the image processing device to obtain a high resolution polarization image; and based on the obtained high-resolution polarized image, carrying out object identification and classification by using an automatic identification algorithm.
In an embodiment according to the invention, the receiving antenna array and the detector array are both two-dimensional arrays. It will be appreciated that the receive antenna array and the detector array may also be a one-dimensional array. In the case that the receiving antenna array and the detector array are both one-dimensional arrays, the millimeter wave terahertz imaging device further comprises a rotatable scanning mirror arranged between the focusing lens and the object to be detected. The function and operation of the rotatable scanning mirror has been described in detail above and will not be described further.
In an embodiment according to the present invention, in a case where the receiving antenna array and the detector array are both two-dimensional arrays, a method of processing the polarization image by the image processing apparatus to obtain a high-resolution polarization image, that is, a method of image demosaicing processing will be described in detail. In this embodiment, the antenna array includes a plurality of macro-pixel units, each macro-pixel unit includes N receiving antennas, the N receiving antennas have at least N-1 polarization angles, and the detector array includes sensing units (N is a positive integer greater than or equal to 4) whose number is equal to that of the receiving antennas and whose positions correspond to each other.
In this embodiment, the polarized image is processed by the image processing device to obtain a high-resolution polarized image, so as to complete the demosaicing process of the original image, and the process includes the following 5 steps. In step S1, in the polarization image obtained by the detector array (for example, as shown in fig. 9), N low-resolution polarization images (for example, 4 images shown in (a), (b), (c), (d) of fig. 10) each having a polarization angle and including all the pixels having the same polarization angle are extracted from the pixels corresponding to the plurality of sensing elements. For example, as shown in fig. 9, the detector array employed comprises 16 sensing units, and thus the resolution of the obtained polarization image is 4 × 4. The antenna array corresponding to the detector array comprises 16 receiving antennas, so that the size of the antenna array is 4 x 4, the polarization angles of the macro pixel units of the antenna array are-45-degree linear polarization, 0-degree linear polarization, 45-degree linear polarization and 90-degree linear polarization respectively, and the resolution of the macro pixel units is 2 x 2. Therefore, as shown in fig. 10, the 4 low-resolution polarization images obtained by step S1 each have a resolution of 2 × 2, and (a) the polarization angle of the image is 0 °, (b) the polarization angle of the image is 45 °, (c) the polarization angle of the image is 90 °, and (d) the polarization angle of the image is-45 °.
in step S2, the non-polarized intensity data of the pixel at the polarization angle position in the polarization array is estimated to obtain a high-resolution non-polarized image, and the size of the high-resolution non-polarized image is equal to the size of the antenna array. And averaging the estimated non-polarized intensity data in each polarized unit of the high-resolution non-polarized image, wherein the average value is used as a non-polarized intensity value of each polarized unit with a corresponding polarization angle, and the same processing is carried out in the whole array range to obtain N low-resolution non-polarized images. As shown in fig. 10, in the illustrated embodiment, the resolution of the high resolution non-polarized image is 4 x 4, the number of low resolution non-polarized images is 4 and the resolution is 2 x 2.
At step S3, under the guidance of the N low-resolution images obtained in step S1 and the low-resolution non-polarized images obtained in step S2, obtaining N intermediate images with different polarization angles through interpolation, and then subtracting the low-resolution non-polarized images from the N intermediate images to obtain N low-resolution polarization difference images; as shown in FIG. 10, in the illustrated embodiment, 4 low resolution polarization difference images with a resolution of 2 x 2 were obtained
In step S4, the N low-resolution polarization difference images obtained in step S3 are processed by using a bilinear difference value and upsampling processing method, so as to obtain N corresponding high-resolution polarization difference images. As shown in fig. 10, in the illustrated embodiment, 4 high resolution polarization difference images with a resolution of 4 x 4 were obtained.
At step S5, the N high-resolution polarization difference images obtained at step S4 are summed with the high-resolution non-polarized image obtained at step S2, and finally N high-resolution polarized images are obtained. As shown in fig. 10, in the illustrated embodiment, 4 high resolution polarized images are obtained.
In an embodiment according to the present invention, in order to further improve the resolution of the high-resolution polarization image, a super-resolution image processing algorithm may be performed on the high-resolution polarization image with polarization information to improve the resolution. Super-resolution imaging can be realized through a super-resolution polarization imaging reconstruction algorithm, the resolution ratio is improved by at least 4 times compared with the existing imaging image mode (polarization information cannot be obtained), and the resolution ratio can reach a millimeter level. This is very effective for identifying suspicious structures on a millimeter level.
It will be appreciated by those skilled in the art that the embodiments described above are exemplary and can be modified by those skilled in the art, and that the structures described in the various embodiments can be freely combined without conflict in structure or principle.
Having described preferred embodiments of the present disclosure in detail, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope and spirit of the appended claims, and the disclosure is not limited to the exemplary embodiments set forth herein.
Claims (11)
1. A millimeter wave terahertz imaging device for safety inspection of an object to be inspected, which comprises a focusing lens, a detector and a graphic processing device,
the focusing lens is arranged between the detected object and the detector and is configured to focus the millimeter wave terahertz waves which are spontaneously radiated or reflected by the detected object on the detector;
A detector including an antenna array and a detector array, wherein the antenna array is disposed on a side of the detector array facing the focusing lens and is disposed as an antenna port of the detector array, and the detector array is disposed on a focal plane of the focusing lens and is configured to convert millimeter wave terahertz waves received by the antenna array into a polarized image of a detected object; and
The image processing device is arranged on one side of the detector array far away from the antenna array and is configured to process the polarization image to identify and classify the detected object.
2. The millimeter wave terahertz imaging device of claim 1, wherein the antenna array comprises a plurality of receive antennas, each of the plurality of receive antennas having a particular polarization direction.
3. The millimeter wave terahertz imaging device according to claim 2, wherein the detector array comprises a plurality of wave sensing units, the number of the plurality of wave sensing units is the same as that of the plurality of receiving antennas, and the position of each wave sensing unit on the detector array corresponds to the position of each receiving antenna on the antenna array.
4. The millimeter wave terahertz imaging device according to claim 1, wherein the antenna array is a one-dimensional antenna array, the detector array is a one-dimensional detector array, the one-dimensional antenna array comprises a plurality of macro-pixel units arranged linearly, wherein each macro-pixel unit is an N x 1 antenna array, wherein N is a positive integer, N is greater than or equal to 3, and each macro-pixel unit comprises at least N-1 different polarization angles.
5. The millimeter wave terahertz imaging device of claim 1, wherein the antenna array is a two-dimensional antenna array, the detector array is a two-dimensional detector array, the two-dimensional antenna array comprises a plurality of macro-pixel cells arranged on a two-dimensional plane, wherein each macro-pixel cell is M1*M2Of antenna array, wherein M1，M2Is a positive integer, and M1，M2≧ 2, and each macropixel unit includes at least N-1 different polarization angles, where N ═ M1*M2。
6. The millimeter wave terahertz imaging device according to claim 4 or 5, wherein the N receiving antennas of each macro-pixel unit comprise at least one of: n linearly polarized receiving antennas; n-1 linear polarization receiving antennas and a circular polarization receiving antenna.
7. The millimeter wave terahertz imaging apparatus of claim 6, wherein the polarization angles of the N linearly polarized receiving antennas are Deg1, Deg2, Deg3, … DegN, respectively, wherein
Wherein i is a positive integer less than or equal to N.
8. The millimeter wave terahertz imaging apparatus of claim 6, wherein the polarization angles of the N-1 linearly polarized receiving antennas are Deg1, Deg2, Deg3, … DegN-1, respectively, wherein
Or
Wherein i is a positive integer less than or equal to N-1;
Wherein the circular polarization includes at least one of left-hand circular polarization and right-hand circular polarization.
9. The millimeter wave terahertz imaging apparatus according to claim 1, further comprising a millimeter wave terahertz radiation source for radiating millimeter wave terahertz waves to the object to be inspected.
10. The millimeter wave terahertz imaging apparatus according to claim 1, wherein the antenna array is a one-dimensional antenna array, the detector array is a one-dimensional detector array, and the millimeter wave terahertz imaging apparatus further comprises a rotatable scanning mirror disposed in an optical path between the object to be inspected and the focusing lens.
11. The millimeter wave terahertz imaging apparatus according to claim 10, wherein the rotatable scanning mirror is rotatable to image a specific portion on the object to be inspected on a specific wave sensing unit of the one-dimensional detector array at one specific rotation angle.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109471195A (en) * | 2018-12-29 | 2019-03-15 | 同方威视技术股份有限公司 | Millimeter wave terahertz imaging equipment and object identification classification method |
| CN111352170A (en) * | 2020-03-09 | 2020-06-30 | 浙江云特森科技有限公司 | Sectional scanning method |
| CN111505629A (en) * | 2020-05-08 | 2020-08-07 | 中国科学院国家空间科学中心 | Terahertz security inspection imaging system and method |
| CN113008907A (en) * | 2019-12-19 | 2021-06-22 | 华为技术有限公司 | Terahertz sensing system and terahertz sensing array |
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| CN109471195A (en) * | 2018-12-29 | 2019-03-15 | 同方威视技术股份有限公司 | Millimeter wave terahertz imaging equipment and object identification classification method |
| CN109471195B (en) * | 2018-12-29 | 2023-11-10 | 同方威视技术股份有限公司 | Millimeter wave terahertz imaging device and object identification and classification method |
| CN113008907A (en) * | 2019-12-19 | 2021-06-22 | 华为技术有限公司 | Terahertz sensing system and terahertz sensing array |
| CN113008907B (en) * | 2019-12-19 | 2024-04-12 | 华为技术有限公司 | Terahertz sensing system and terahertz sensing array |
| CN111352170A (en) * | 2020-03-09 | 2020-06-30 | 浙江云特森科技有限公司 | Sectional scanning method |
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