A passive millimeter wave terahertz three-dimensional imaging system based on a fresnel lens

Abstract

The application provides a passive millimeter wave terahertz three-dimensional imaging system based on a Fresnel lens, which can solve the problems that a single device cannot meet the three-dimensional imaging requirements, and multiple devices occupy a large space and have high costs. The system comprises a scanning mirror, a scanning device for controlling the scanning mirror to scan a detected area and feeding back scanning position information to an electronic processing device to realize scanning imaging of the detected area, a non-confocal surface quasi-optical device based on a Fresnel lens composed of multiple Fresnel unit lenses, a detector group for detecting and receiving terahertz radiation signals collected by the non-confocal surface quasi-optical device based on the Fresnel lens and outputting the received terahertz radiation signals to the electronic processing device, and an electronic processing device for filtering, amplifying, sampling and digital image processing of the terahertz radiation signals output by the detector group and controlling and receiving feedback of the scanning device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of security inspection technology, in particular to the field of passive terahertz imaging system, and specifically to a passive millimeter wave terahertz three-dimensional imaging system based on a Fresnel lens. BACKGROUND

[0002] For a long time, the equipment for security inspection in personnel-intensive places such as airports and railways mainly consists of X-ray luggage inspection equipment and metal security gates or handheld metal detector type human body inspection equipment. The X-ray luggage inspection equipment performs excellently in the inspection of luggage items, but due to the ionizing effect of X-rays, it can cause harm to the human body, so it is only suitable for inspecting items, but not suitable for inspecting the human body. The metal detector can effectively detect metal products, but it cannot detect non-metallic items carried in the clothes of the human body. Although the method of using a metal detector in combination with manual inspection can detect dangerous items carried by the human body to some extent, it has the problems of slow security inspection speed, easy missed detection of non-metallic dangerous items, and invasion of the privacy of the human body. There is a lack of a security inspection method that can detect hidden dangerous items carried by the human body without causing harm to the human body.

[0003] In the past decade, with the development of technology, the emergence of passive terahertz security inspection equipment has solved the above problems. The passive terahertz human body security inspection equipment realizes imaging by receiving the electromagnetic radiation of the terahertz wave band of the object being measured, accurately judges the position and shape of the dangerous items carried by the human body, and helps security personnel make better judgments. However, the passive imaging technology millimeter wave / terahertz imaging system currently used can only obtain two-dimensional information of the imaged target, and cannot obtain depth information, so it cannot perform three-dimensional imaging of the target. However, when imaging is performed only using two-dimensional information, it is easy to cause misjudgment in the identification of the object without obtaining the depth (thickness) information of the object. In order to solve this problem, currently there are passive terahertz three-dimensional imaging detection methods that use multiple devices in combination, such as Chinese Patent for Invention No. CNCN110411375B, which discloses a three-dimensional imaging method based on passive millimeter wave / terahertz imaging technology. The method uses two identical passive millimeter wave / terahertz imaging systems to image the same target respectively, uses image registration technology to obtain the position information of the same target point in the images of the two imaging systems, combines the installation distance and angle information between the two imaging systems, and calculates the three-dimensional coordinate point through a three-dimensional coordinate calculation formula, so as to obtain the depth information of the target and realize three-dimensional imaging of the target by the passive millimeter wave / terahertz imaging system. Although this method can realize three-dimensional imaging, it requires the use of two devices in combination, so there are problems of large space occupation of the equipment and high cost of the equipment in actual application. SUMMARY

[0004] In order to solve the above problems, the application provides a passive millimeter wave terahertz three-dimensional imaging system based on a Fresnel lens, which can solve the problems that a single device cannot meet the three-dimensional imaging requirements, and multiple devices occupy a large space and have high costs.

[0005] The technical scheme is a passive millimeter wave terahertz three-dimensional imaging system based on a Fresnel lens, characterized in that it comprises a scanning mirror, a scanning device, an optical device, a detector group and an electronic processing device, the scanning device is connected with the scanning mirror and the electronic processing device, and the detector group is connected with the electronic processing device.

[0006] The scanning mirror is used for scanning a detected area and receiving a terahertz radiation signal returned from the detected area.

[0007] The scanning device controls the scanning mirror to scan the detected area and feeds back scanning position information to the electronic processing device, so as to realize scanning imaging of the detected area.

[0008] The optical device is used for receiving the terahertz radiation signal reflected from the scanning mirror and concentrating the signal.

[0009] The detector group is used for detecting and receiving the terahertz radiation signal concentrated by the optical device, and outputs the received terahertz radiation signal to the electronic processing device.

[0010] The electronic processing device is used for filtering, amplifying, sampling and digital image processing of the terahertz radiation signal output by the detector group, and controls and receives feedback of the scanning device.

[0011] The optical device is a non-confocal plane quasi-optical device based on a Fresnel lens, which is a lens array composed of at least two groups of Fresnel lens groups with different focal lengths, and each Fresnel lens group is composed of at least one Fresnel unit lens array.

[0012] Further preferably, the at least two groups of Fresnel lens groups with different focal lengths are arranged in a columnar and adjacent manner to form the lens array.

[0013] Further, the number of the detector group is the same as the number of the Fresnel lens group of the non-confocal plane quasi-optical device.

[0014] Further preferably, the at least two groups of Fresnel lens groups with different focal lengths are arranged in a columnar and adjacent manner to form the lens array.

[0015] The system has the advantages that: the non-confocal plane quasi-optical device based on the Fresnel lens is adopted, the lens array is composed of at least two groups of Fresnel lens groups with different focal lengths, and the Fresnel lens group is composed of at least one Fresnel unit lens array, so that different angle imaging of the detected area can be realized by only one passive millimeter wave / terahertz imaging system, and then three-dimensional imaging of the detected area can be realized by fusing multi-angle images, so that the problems of large space occupation of equipment and high cost of equipment in actual application can be effectively reduced; and the at least two groups of Fresnel lens groups with different focal lengths are arranged in a column adjacent manner to form the lens array, so as to establish the corresponding relationship between the detector and the lens and the position relationship between the specific measured points in the detected area and the corresponding points on the imaging image, so as to simplify the design of the whole three-dimensional imaging system; in addition, the arrangement of the Fresnel unit lenses of the at least two groups of Fresnel lens groups with different focal lengths in the honeycomb structure form can make the arrangement of the lens array more compact, the overall structure tend to be more simple and easy to process, and the light utilization rate, three-dimensional imaging precision and effect can be improved as much as possible. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A system configuration schematic diagram of the passive millimeter wave terahertz three-dimensional imaging system based on the Fresnel lens is shown in the figure.

[0017] Figure 2 A arrangement schematic diagram of the multiple Fresnel lenses of the non-confocal plane quasi-optical device in the system in a honeycomb structure is shown in the figure. DETAILED DESCRIPTION

[0018] See Figure 1 The passive millimeter wave terahertz three-dimensional imaging system based on the Fresnel lens includes a scanning mirror, a scanning device, an optical device, a detector group and an electronic processing device,

[0019] The scanning mirror is used for scanning the detected area and receiving the terahertz radiation signal returned from the detected area.

[0020] The scanning device is connected with the scanning mirror and the electronic processing device respectively, and is used for controlling the scanning mirror to scan the detected area and feeding back the scanning position information to the electronic processing device, so as to realize the scanning imaging of the detected area.

[0021] The optical device for receiving and collecting the terahertz radiation signal reflected from the scanning mirror comprises at least two groups of Fresnel lens groups with different focal lengths, and the Fresnel lens group is arranged by at least one Fresnel unit lens array, and the at least two groups of Fresnel lens groups constitute the lens array; in the embodiment, the optical device is composed of five groups of Fresnel lens groups, wherein the three Fresnel unit lenses numbered as 3, 4 and 5 form the first group of Fresnel lens groups with a focal length f1, the four Fresnel unit lenses numbered as 2, 14, 15 and 6 form the second group of Fresnel lens groups with a focal length f2, the five Fresnel unit lenses numbered as 1, 13, 19, 16 and 7 form the third group of Fresnel lens groups with a focal length f3, the four Fresnel unit lenses numbered as 12, 18, 17 and 8 form the fourth group of Fresnel lens groups with a focal length f4, and the three Fresnel unit lenses numbered as 11, 10 and 9 form the fifth group of Fresnel lens groups with a focal length f5, and the focal length f1, the focal length f2, the focal length f3, the focal length f4 and the focal length f5 are all different.

[0022] The detector group is composed of a plurality of single detectors and is connected with the electronic processing device respectively, each single detector is used for detecting and receiving the terahertz radiation signal collected by the optical device, and outputs the received terahertz radiation signal to the electronic processing device.

[0023] The electronic processing device is used for filtering, amplifying, sampling and digital image processing on the terahertz radiation signal output by each single detector of the detector group, and controls the scanning device and receives the scanning position information fed back by the scanning device.

[0024] As a preferred technical scheme of the system, the number of the detector group is the same as the number of the Fresnel lens groups with different focal lengths in the non-confocal surface quasi-optical device; in the embodiment, five groups of Fresnel lens groups with different focal lengths are arranged, and therefore five groups of detector groups are arranged. Moreover, the number of the single detector in each group of detector groups is determined by the design parameters such as the spot of the actual unit lens and the size of the detector horn antenna.

[0025] The passive millimeter wave terahertz three-dimensional imaging system has at least two groups of Fresnel lens groups with different focal lengths to constitute the lens array, and each Fresnel lens group is arranged by at least one Fresnel unit lens array, so that the detected area can be scanned and imaged at multiple angles by only one passive millimeter wave / terahertz imaging system, and then the three-dimensional scanning imaging of the same detected area can be realized by fusing the multi-angle imaging data, so that the problems of large space occupation and high equipment cost in actual application can be effectively reduced.

[0026] As a preferred technical scheme of the system, the at least two groups of Fresnel lens groups with different focal lengths are arranged in a column adjacent manner according to different focal lengths to establish the corresponding relationship between the detector and the lens and the position relationship between the specific measured points in the detected area and the corresponding points on the imaged image, thereby simplifying the design of the whole three-dimensional imaging system. Figure 2 In the embodiment, the lens array comprises the aforementioned five groups of Fresnel lens groups arranged in a column adjacent manner.

[0027] As a further preferred technical scheme of the system, the Fresnel unit lenses of the at least two groups of Fresnel lens groups with different focal lengths are arranged in a honeycomb structure to make the arrangement of the lens array more compact, the overall structure simpler and easier to process, and to improve the light utilization rate, the three-dimensional imaging precision and effect as much as possible. In the embodiment, the nineteen Fresnel unit lenses numbered 1 to 19 are arranged in a honeycomb structure while being arranged in a column adjacent manner according to five different focal lengths (focal length f1, focal length f2, focal length f3, focal length f4 and focal length f5).

[0028] The application of the Fresnel lens to the terahertz three-dimensional imaging system field has good portability and can not only meet the requirements of terahertz passive imaging, millimeter wave passive imaging and even far infrared passive imaging.

[0029] Although the application is disclosed in the above preferred embodiments, it is not intended to limit the application, and any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the application. Therefore, any modification, equivalent change and modification of the above embodiments according to the technical essence of the application, which does not depart from the technical scheme of the application, falls within the protection scope defined by the claims of the application.

[0030] It is obvious for those skilled in the art that the application is not limited to the details of the above exemplary embodiments, and the application can be realized in other specific forms without departing from the spirit or basic characteristics of the application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the application is defined by the appended claims rather than the above description, and it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims. Any reference signs in the claims should not be regarded as limiting the claims.

[0031] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature described. The specification can include implicit combinations of explicitly mentioned features and / or explicit combinations of implicitely mentioned features. Each embodiment depends on the explicit combinations of features and / or the implicit combinations of features made specifically within that embodiment, and each such embodiment can be combined with every other such embodiment to create further embodiments.

Claims

1. A passive millimeter-wave terahertz three-dimensional imaging system based on a Fresnel lens, characterized by: It includes a scanning mirror, a scanning device, an optical device, a detector group and an electronic processing device, the scanning device is connected with the scanning mirror and the electronic processing device respectively, the detector group is connected with the electronic processing device; wherein, The scanning mirror is used for scanning the detected area and receiving the terahertz radiation signal returned from the detected area; The scanning device controls the scanning mirror to scan the detected area and feeds back the scanning position information to the electronic processing device, so as to realize the scanning imaging of the detected area; The optical device is used for receiving the terahertz radiation signal reflected by the scanning mirror and gathering the signal; The detector group is used for detecting and receiving the terahertz radiation signal gathered by the optical device, and outputting the received terahertz radiation signal to the electronic processing device; The electronic processing device is used for filtering, amplifying, sampling and digital image processing of the terahertz radiation signal output by the detector group, and controlling and receiving feedback of the scanning device; The optical device is a non-confocal plane optical device based on Fresnel lens, which is a lens array composed of at least two groups of Fresnel lens groups with different focal lengths, and each Fresnel lens group is composed of at least one Fresnel unit lens array; The at least two groups of Fresnel lens groups with different focal lengths are arranged in a column adjacent manner to form the lens array; Each Fresnel unit lens of the at least two groups of Fresnel lens groups with different focal lengths is arranged in a honeycomb structure to form the lens array.

2. The Fresnel lens based passive millimeter wave / terahertz three-dimensional imaging system according to claim 1, characterized in that: The number of the detector group is the same as the number of the Fresnel lens group of the non-confocal plane optical device.

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