Imaging device, imaging method, and computer program

Abstract

To provide an imaging apparatus, an imaging method, and a computer program for creating a composite image suitable for inspection or the like of a moving object.SOLUTION: An imaging apparatus has: irradiation means S403 that irradiates an object with a terahertz wave; first imaging means S405 that picks up an image of a reflected wave from the object irradiated by the irradiation means with the terahertz wave; imaging signal processing means S407 that processes an imaging signal obtained from the first imaging means to generate a first image signal; image processing means S410 that combines a plurality of first image signals to generate a composite image; and control means that causes the first imaging means to perform imaging multiple times during movement of the object and causes the imaging signal processing means to generate a plurality of first image signals, and causes the image processing means to select and combine the plurality of first image signals to generate a composite image.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an imaging device, an imaging method, a computer program, etc. that use terahertz waves. [Background technology]

[0002] Inspection technology using terahertz waves is known. Terahertz waves are defined as electromagnetic waves having a frequency of 30 GHz or more and 30 THz or less. Patent Document 1 discloses an inspection system that uses terahertz waves to inspect the interior of a moving object. This system is configured to irradiate the inspection object with terahertz waves and acquire a terahertz wave image from the reflected waves. From the acquired image, personal belongings are identified using image recognition. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-190951 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional technology disclosed in the above-mentioned Patent Document 1 has the advantage of being able to inspect moving objects, but it does not take into account the characteristic of terahertz waves, which is that the specular reflection component is strong, so there is a risk that areas may not be inspected. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an imaging device or the like that generates a composite image suitable for inspecting a moving object or the like. [Means for solving the problem]

[0005] An imaging device according to one aspect of the present invention comprises: an irradiation means for irradiating a target with terahertz waves; a first imaging means for imaging a reflected wave from the object irradiated with the terahertz wave by the irradiation means; The imaging signal obtained from the first imaging means is processed to generate a first image signal. and at the same time, performing image recognition of a predetermined first object from the first image signal. imaging signal processing means; an image processing means for synthesizing a plurality of the first image signals to generate a composite image; a control means for capturing images of the object multiple times using the first imaging means while the object is moving, generating multiple first image signals using the imaging signal processing means, and for generating a composite image by selecting and combining the multiple first image signals using the image processing means; death, The control means adjusts at least one of the size and the position of the first object in the first image signals, and then combines the first image signals obtained by capturing images of the object as a moving inspection target at different positions using the first imaging means. It is characterized by the following. [Effects of the Invention]

[0006] According to the present invention, it is possible to realize an imaging device or the like that generates a composite image suitable for inspecting a moving object or the like. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a functional block diagram illustrating a configuration of an imaging device according to a first embodiment of the present invention. [Figure 2] 1A and 1B are diagrams showing a gate system in which an imaging device according to a first embodiment of the present invention is arranged, where 1A is a front view of the gate system and 1B is a top view of the gate system. [Figure 3] 1 is a diagram illustrating an optical path of a terahertz wave in a gate system in which an imaging device 100 according to a first embodiment of the present invention is installed. [Figure 4] (A) is a diagram showing an image captured using visible light, (B) is an image captured using terahertz waves, and (C) is an illustration of a composite image combining a visible light image and a terahertz wave image. [Figure 5] 10A and 10B are diagrams illustrating terahertz wave images captured when an object 300 moves in a gate system in which an imaging device is installed. [Figure 6] FIG. 2 is a diagram illustrating details of a gate system 200 according to a first embodiment of the present invention. [Figure 7] 10 is a flowchart illustrating a processing flow of the gate system 200 according to the first embodiment of the present invention. [Figure 8] 10 is a flowchart illustrating a processing flow of a gate system 200 according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a diagram illustrating a gate system 200 according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, preferred embodiments of the present invention will be described by way of example with reference to the accompanying drawings. In each drawing, the same members or elements are designated by the same reference numerals, and duplicated descriptions will be omitted or simplified. [Example]

[0009] The terahertz wave region, roughly defined as 30 GHz or higher and 30 THz or lower, has properties different from visible light depending on its wavelength. Its characteristic of high linearity and moderate transparency allows for a variety of applications, and in the field of imaging, it is expected to be used for high-resolution, non-destructive, non-contact imaging on the order of millimeters. This example describes an example of an imaging device for inspection that can capture images of the surface or interior of an object non-destructively and non-contactly.

[0010] Fig. 1 is a functional block diagram showing the configuration of an imaging device according to a first embodiment of the present invention. In Fig. 1, the imaging device 100 includes a visible light camera 109, an imaging unit 110, an imaging control unit 111, an imaging signal processing unit 112, an image recording unit 113, an image processing unit 114, and a display unit 115. The imaging device 100 further includes an illumination unit 120, an illumination control unit 121, an object detection sensor 122, a distance measurement unit 123, a control unit 130, etc.

[0011] 1 may be realized by causing a computer (not shown) included in the imaging device 100 to execute a computer program stored in a memory (not shown) serving as a storage medium. Alternatively, some or all of the functional blocks may be realized by hardware. Examples of hardware that can be used include a dedicated circuit (ASIC) and a processor (reconfigurable processor, DSP). Furthermore, the functional blocks shown in FIG. 1 do not have to be housed in the same housing, but may be provided in separate devices connected to each other via signal paths.

[0012] The imaging device 100 has a visible light camera 109 (second imaging means) for capturing an image of an object using visible light, and the visible light camera 109 includes an optical system and an imaging element such as a CMOS image sensor. The visible light camera 109 also has an adjustment unit for adjusting the F-number and shutter speed (imaging time) to adjust the depth of field and exposure time. The adjustment unit is configured to perform various adjustment operations in response to control signals from the control unit 130.

[0013] The imaging device 100 also includes an irradiation unit 120 as irradiation means for irradiating an object with terahertz waves, and an imaging unit 110 as first imaging means for imaging a wave reflected from the object 300 irradiated with terahertz waves by the irradiation means. The irradiation unit 120 includes an oscillator that generates terahertz waves, and the imaging unit 110 includes an imaging sensor that is highly sensitive to terahertz waves. The operation states of the imaging unit 110 and the irradiation unit 120 are controlled by an imaging control unit 111 and an irradiation control unit 121, respectively.

[0014] The imaging device 100 has an imaging signal processing unit 112 that processes imaging signals obtained from the visible light camera 109 and imaging unit 110. The imaging signal processing unit 112 converts the imaging signals into image signals through signal processing, and also performs image processing such as noise removal and edge extraction. Here, the imaging signal processing unit 112 functions as imaging signal processing means that processes the imaging signals obtained from the first imaging means to generate a first image signal, and processes the imaging signals obtained from the second imaging means to generate a second image signal.

[0015] Furthermore, the imaging signal processing unit 112 can recognize a predetermined object from the image signal from the visible light camera 109 or the imaging unit 110 by image recognition. That is, the imaging signal processing unit 112 is configured to be able to recognize that a specific first object (e.g., a dangerous object or a prohibited item) is included in the first image signal. Furthermore, the imaging signal processing unit 112 is configured to be able to recognize a predetermined second object (e.g., a predetermined person) from the second image signal.

[0016] The image recording unit 113 records the image signals generated by the imaging signal processing unit 112. The image processing unit 114 selects and combines the image signals of the inspection object from the multiple first and second image signals recorded in the image recording unit 113 so that there is no overlap or lack of image signals for the inspection object. As will be described later, the imaging signals acquired by the imaging unit 110 are partial (fragmentary) depending on the position of the inspection object. Therefore, in this embodiment, images of a moving object as an inspection object are taken at different positions, and the multiple image signals obtained thereby are combined.

[0017] That is, the image processing unit 114 combines a plurality of first image signals captured partially (fragmentarily) to form a single overall image. Therefore, while there are cases where it is not possible to correctly recognize whether each of the first image signals captured fragmentarily is, for example, a first object, by combining them to form a single overall image, the possibility of correct recognition increases. Here, the image processing unit 114 functions as an image processing unit that synthesizes a plurality of first image signals output from the first imaging unit to generate a composite image.

[0018] When the above-mentioned synthesis is performed, suitable first image signals are selected from the plurality of first image signals recorded in the image recording unit 113 so that there are no overlaps or omissions, and synthesis is performed. Also, any first image signal is enlarged or reduced by the image processing unit 114 so that the size of the first object in the first first image signal is approximately the same as the size of the first image signal in the second and subsequent first image signals. As a result, the sizes of the first objects are adjusted to be approximately the same before synthesis.

[0019] Furthermore, for example, the image processing unit 114 performs image processing for adjusting the image position for any first image signal so that the position of the first object in the first image signal for the first frame and the position of the first object in the first image signals for the second frame and thereafter are approximately the same, before combining. This makes it possible to prevent the size and position of the combined image from being distorted. As described above, this embodiment is characterized in that at least one of the size and position of the first object is adjusted before synthesis.

[0020] Furthermore, the image processing unit 114 can also combine a plurality of first image signals with a second image signal. In this case, the image processing unit 114 adjusts at least one of the size and position of the second object in the second image signal, and then combines the plurality of first image signals with the second image signal. In this case, the image processing unit 114 may enlarge or reduce the second image signal to adjust the size of the second object, or may perform image processing on the second image signal to adjust the position of the second object. These operations will be described later.

[0021] Note that the term "combining" here may refer to combining multiple images into one image, or may refer to combining, for example, N images into M images, where M is a number less than N. Alternatively, for example, if a predetermined dangerous object or prohibited item appears in only one of multiple images captured with terahertz waves, a first image signal of that image may be combined with a second image signal of visible light of object 300 at the time the first image signal was captured. The image processing unit 114 can also directly process the image signals from the visible light camera 109 and the imaging unit 110 that have been processed by the imaging signal processing unit 112 for display on a monitor.

[0022] The imaging control unit 111 controls the imaging unit 110 etc. As with the visible light camera 109, the imaging unit 110 can adjust the depth of field and exposure time by adjusting the F-number and shutter speed (imaging time etc.). Furthermore, the irradiation control unit 121 can control the irradiation intensity and irradiation timing of the irradiation unit 120. The control unit 130 controls the imaging control unit 111 and the irradiation control unit 121 in synchronization with each other to prevent overexposure and save power.

[0023] The control unit 130 has a built-in CPU as a computer, and functions as a control means for controlling the operation of each part of the entire apparatus based on a computer program stored in a memory as a storage medium. The display unit 115 displays the image data processed by the image processing unit 114. Alternatively, the display unit 115 may display the results of image recognition by the imaging signal processing unit 112.

[0024] For example, if the imaging signal processing unit 112 recognizes an image of a specific first object (such as a dangerous object or a prohibited item) in the first image signal, the display unit 105 may be configured to promptly notify the user that the first object has been recognized and display a warning. The object detection sensor 122 is a sensor that detects that an object 300 has entered the gate, and the distance measurement unit 123 is a unit that measures the distance of the object that has entered the gate. The operations of the object detection sensor 122 and the distance measurement unit 123 will be described later.

[0025] 2A and 2B are diagrams showing a gate system in which an imaging device according to the first embodiment of the present invention is arranged, where (A) is a front view of the gate system and (B) is a top view of the gate system. Gate systems include baggage inspection gates at airport security stations and gates for controlling building entrances and exits.

[0026] 2, imaging units 110a and 110b and illumination units 120a and 120b are installed at the gate. The imaging units 110a and 110b each correspond to the imaging unit 110 in FIG. 1, and the illumination units 120a and 120b each correspond to the illumination unit 120 in FIG. 1.

[0027] 2(A), an irradiation unit 120a is disposed at the gate 200a on the left side, and an irradiation unit 120b is disposed at the gate 200b on the right side, irradiating the object 300 from the left and right. The object 300 illuminated by the irradiation units 120a and 120b is photographed by, for example, an imaging unit 110a disposed at the gate 200a on the left side, and an imaging unit 110b disposed at the gate 200b on the right side, respectively. However, the number and arrangement of the imaging units 110a and 110b and the irradiation units 120a and 120b are not limited to the example in FIG. 2.

[0028] 2(B), an object 300 moves from the top to the bottom of the drawing through a gate system 200 equipped with imaging units 110a and 110b and illumination units 120a and 120b. The moving object 300 is illuminated by illumination units 120a and 120b, and photographed by imaging units 110a and 110b.

[0029] Furthermore, terahertz waves have different properties from visible light due to their wavelength, and therefore the imaging method differs from that of visible light. That is, as mentioned above, terahertz waves belong to a frequency band of roughly 30 GHz or more and 30 THz or less, and have wavelengths of about 10 μm to 1 mm, making them electromagnetic waves that are longer than the wavelength of visible light. Generally, the reflection of electromagnetic waves is not diffused by irregularities smaller than the wavelength. Therefore, diffusion does not occur on irregularities smaller than the wavelength, and specular reflection becomes the main reflection. Therefore, in this embodiment, the target object 300 is irradiated with terahertz waves, and the specular reflection component is photographed.

[0030] FIG. 3 is a diagram illustrating the optical path of the terahertz wave in the gate system in which the imaging device 100 according to the first embodiment of the present invention is installed. 3 shows the optical path of terahertz waves irradiated by irradiation units 120a and 120b, specularly reflected by object 300, and reaching imaging units 110a and 110b. Specular reflection is a reflection in which the angle of incidence and the angle of reflection are equal.

[0031] 3A shows the optical path when terahertz waves are incident perpendicularly on a part of object 300. The terahertz waves irradiated from irradiation unit 120a are incident almost perpendicularly on a part of object 300, are specularly reflected off the part of object 300, and are then incident on imaging unit 110a almost perpendicularly. The reflected terahertz waves are then captured by imaging unit 110a.

[0032] 3(B) shows the optical path when terahertz waves are incident at an oblique angle on object 300. The terahertz waves irradiated from irradiation unit 120a are incident on object 300 at an oblique angle, and are reflected at the same reflection angle as the incident angle due to specular reflection from a part of object 300. The reflected waves are incident on imaging unit 110b, and a terahertz wave image is captured.

[0033] As described above, when creating an image using specular reflection, due to the characteristics of specular reflection, the reflective surface of the object 300 is photographed so that the angle of incidence and the angle of reflection are the same, and therefore the angle of the reflective surface of the object 300 that can be photographed is determined by the positions of the illumination unit and the imaging unit.

[0034] That is, in order to capture images of multiple reflective surfaces of the object 300, it is necessary to change the positions of the irradiation unit and the imaging unit and the angles of the reflective surfaces of the object 300. In this embodiment, images of multiple reflective surfaces are captured by utilizing the fact that the object 300 moves within the gate of the gate system 200, and the positional relationship between the irradiation unit, the imaging unit, and the object 300 changes.

[0035] Figure 4(A) shows an image captured by a visible light camera, (B) shows an image captured using terahertz waves, and (C) shows an image of a composite image created by combining a visible light image and a terahertz wave image. For example, suppose that the object 300 is hiding a knife under its clothes. As shown in Fig. 4(A), in the visible light image, the knife is hidden under the clothes and therefore cannot be seen from the outside.

[0036] In the terahertz wave image in Figure 4(B), the intensity is high only in the area of ​​the knife, making it clear that the person is holding a knife. Figure 4(C) shows a composite image that combines a visible light image and a terahertz wave image, and the composite image makes it possible to identify where the person in question is hiding a dangerous object such as a knife.

[0037] Next, imaging of a moving object 300 in the first embodiment of the present invention will be described with reference to Fig. 5. Fig. 5 is a diagram illustrating a terahertz wave image captured when the object 300 moves in a gate system in which an imaging device is installed. 5(A) and (B) show the optical path of terahertz waves irradiated from irradiation unit 120a, reflected by object 300, and incident on imaging unit 110b when object 300 moves. Figures 5(C) and (D) show the areas that can be imaged with terahertz waves in the states of Figures 5(A) and (B), respectively.

[0038] Fig. 5(A) shows a case where the distances between the imaging units 110a, 110b and the irradiation units 120a, 120b and the object 300 are large. Fig. 5(B) shows a case where the distances between the imaging units 110a, 110b and the irradiation units 120a, 120b and the object 300 are small. 5(A) and 5(B), the optical path of the light rays entering the imaging unit 110 differs depending on the position of the object 300. This is because, as described above, the terahertz wave reflected from the object 300 has a large specular reflection component, and the specular reflection component is captured. When attempting to capture the specular reflection component as the object 300 moves, the reflecting surface changes depending on the position of the object 300. This causes a shift in the capture area in which the reflected terahertz wave can be captured.

[0039] 5(C) and (D) are the photographed areas corresponding to those in FIGS. 5(A) and (B), respectively, and it can be seen that the photographed area in (D) is shifted to the left compared to the photographed area in (C). This is because the photographed area shifted due to the movement of the object 300. In addition, in Figure 5, it is assumed that the right half of the object 300 will be photographed mainly using the imaging unit 110a and the illumination unit 120a, but by using the imaging unit 110b and the illumination unit 120b, it is also possible to photograph the left half of the object 300 mainly.

[0040] Next, Fig. 6 is a diagram illustrating details of the gate system 200 according to the first embodiment of the present invention. In the example shown in Fig. 6, an object detection sensor 122 that detects that an object 300 has entered the gate, and a distance measurement unit 123 that measures the distance between the object 300 and the imaging unit 110 and the irradiation unit 120 are installed in the gate system 200 shown in Fig. 2. Furthermore, a visible light camera 109 is installed in front of the outside of the exit of the gate system 200. Note that the visible light camera 109 may further include multiple visible light cameras 109a, 109b, etc., so that the gate system 200 can be imaged from different angles.

[0041] In the first embodiment shown in Fig. 6, an object detection sensor 122 is placed at the entrance of the gate to detect that an object 300 has entered the gate system 200. If the object 300 is a person, a human sensor such as a pyroelectric sensor may be used, and if it is an object, a photoelectric sensor or the like may be used as a sensor for detecting the object. Alternatively, a distance measurement unit 123, a visible light camera 109, or the like may be used instead.

[0042] 6, the gate system 200 has a ranging unit 123 to measure the distance between the object 300 that has entered the gate system 200 and the imaging unit 110 and illumination unit 120. The ranging unit 123 may be a sensor that measures the time it takes for light to reflect and return, such as a ToF (Time Of Flight) sensor, or may measure the distance using a visible light stereo camera. Alternatively, the ranging output of a ranging unit that is generally provided in the visible light camera 109 may be used.

[0043] Next, Fig. 7 is a flowchart illustrating the processing flow of the gate system 200 in the first embodiment of the present invention. Note that the operation of each step in Fig. 7 is performed by the computer inside the control unit 130 executing a computer program stored in memory.

[0044] When the gate system 200 starts to be used, in step S401, the object detection sensor 122 and the visible light camera 109 are powered on. This starts detecting whether or not an object 300 has entered the gate system 200, and also starts capturing an image using visible light by the visible light camera 109. If it is determined in step S402 that an object 300 has entered the gate, the process proceeds to the next step S403; if not, step S402 is repeated. In step S403, imaging with terahertz waves is started by turning on the power of the imaging unit 110, the irradiation unit 120, and the distance measurement unit 123. This step functions as an irradiation step for irradiating the object with terahertz waves.

[0045] Next, in step S404, the distance between the object 300 and the imaging unit 110 and the illumination unit 120 is measured using the distance measuring unit 123. This is to keep the size of the object 300 constant in the captured image. That is, as the object 300 gets closer to the imaging unit 110 and the illumination unit 120, the size of the object 300 increases relative to the angle of view. In this embodiment, the size of the object 300 within the captured angle of view is calculated based on the distance measured by the distance measuring unit 123, and image processing is performed to make the sizes uniform. This will be described later.

[0046] Next, in step S405, one still image is captured using terahertz waves by the imaging unit 110 and the irradiation unit 120. Here, step S405 functions as a first imaging step for capturing an image of a reflected wave from the object 300 that has been irradiated with terahertz waves in the irradiation step. As described above, the imaging unit captures an image of the part of the object 300 that has been irradiated by the irradiation unit 120. When imaging with terahertz waves in step S405, the imaging position of the optical system of the imaging unit may be adjusted according to the distance measured in step S404.

[0047] Then, in step S406, an imaging signal processing step is executed to process the imaging signal obtained in the first imaging step and generate a first image signal. Furthermore, the distance measured in step S404 is associated with the terahertz wave image data (first image signal) captured in step S405.

[0048] Then, in step S407, an image file for one image is created by adding distance data and time data at the time of shooting to the first image signal as metadata. At this time, the image capturing signal processing unit 112 performs image recognition to check for the presence of a first object (predetermined dangerous objects such as knives or prohibited items), and if the first object is recognized, a warning is immediately displayed on the display unit 115. At this time, an audio warning may also be given.

[0049] As described above, due to the characteristics of terahertz waves, the imaging area of ​​the object 300 changes depending on the positional relationship between the object 300, the imaging unit 110, and the irradiation unit 120. On the other hand, the size of the object 300 within the angle of view changes depending on the distance between the object 300 and the imaging unit 110 and the irradiation unit 120 .

[0050] Therefore, in the subsequent step S410, when combining multiple first images captured with terahertz waves, distance data is added to the first images as metadata so that the first image signal can be enlarged or reduced depending on the distance from the object 300. Furthermore, in step S407, the positions of the object 300 or the first object in the plurality of first image signals may be adjusted by image processing so that the positions in the screen of the object 300 or the first object coincide with each other. Alternatively, the position adjustment may be performed immediately before combining in step S410.

[0051] Next, in step S408, if it is determined that the object 300 has left the gate system 200 based on, for example, the distance measured by the distance measuring unit 123, the process proceeds to step S409. Then, the power to the imaging unit 110, the irradiation unit 120, and the distance measuring unit 123 is turned off, and the process proceeds to step S410. If the result in step S408 is No, steps S404 to S407 are repeated to take images multiple times, create multiple image files, and record them by the image recording unit 113.

[0052] In step S410, a plurality of first image signals suitable for synthesis are read out from a series of a plurality of image files captured during steps S403 to S408 and recorded in image recording unit 113. Then, based on the distance data added to the first image signals, image processing unit 114 reduces or enlarges the terahertz wave images by image processing so that the sizes are approximately the same, and then synthesizes the images and displays them on display unit 115. Here, step S410 functions as an image processing step that generates a synthetic image by selecting and synthesizing a plurality of first image signals.

[0053] As described above, immediately before the synthesis in step S410, the positions of the first image signals may be adjusted to match before the synthesis. In this way, in this embodiment, the size and position of the object 300 or the first object in the multiple first images captured with terahertz waves are aligned, and then the multiple first images captured in different areas are pasted together to form a composite image.

[0054] Therefore, according to this embodiment, a composite image with uniform size and position can be obtained from a plurality of first images captured using terahertz waves. That is, by appropriately combining the fragmented terahertz wave images, an entire image of the terahertz wave image (e.g., three-dimensional data) can be formed, and a composite image that makes it easy to visually recognize the first object can be obtained. Furthermore, when performing image recognition on the composite image, recognition accuracy can be improved. Furthermore, an appropriate composite image can be obtained in which the size and position of the object 300 or the first object are not distorted, thereby improving image quality.

[0055] Furthermore, by adjusting the size of the terahertz wave image and the image from the visible light camera 109 and then combining them, it is possible to display an image such as that shown in FIG. 4(C). As described above, in steps S401 to S410, the control unit 130 as a control means captures images of the object multiple times in the first imaging step while the object is moving, generates multiple first image signals in the imaging signal processing step, and also executes an image processing step in which the multiple first image signals are selected and combined to generate a composite image.

[0056] Furthermore, time data added as metadata to the image file may be used to combine the image from the visible light camera with the terahertz wave image at the time when, for example, a dangerous object or a prohibited item is recognized as an image of the terahertz wave. Furthermore, if the imaging signal processing unit 112 recognizes an image of a predetermined dangerous object or prohibited item such as a knife in step S406, the display unit 115 may continue to notify the user of this at that time and display a warning.

[0057] Alternatively, if the image recognition accuracy is improved by synthesizing fragmentary terahertz wave images in step S410 and a dangerous or prohibited item is recognized for the first time in the image, the display unit 115 may be notified of this and a warning may be displayed. Instead of using the object detection sensor 122, the visible light camera 109 may be used to detect that the object 300 has entered the gate system.

[0058] Also, instead of the distance measurement unit 123, an object detection sensor may be placed near the exit of the gate system, and based on the output of the object detection sensor, the exit of the object 300 from the gate system 200 may be detected in step S408 of FIG. Alternatively, the object 300 may be detected as having exited the gate system 200 by recognizing an image from a visible light camera.

[0059] Furthermore, in step S404 of this embodiment, the distance between the object 300 and the imaging unit is measured by the distance measuring unit 123, but multiple object detection sensors may be arranged, for example, along the direction of travel of the gate, instead of the distance measuring unit 123. The multiple object detection sensors may then detect the position of the object 300 within the gate, and the distance to the imaging unit 110 or the like may be calculated according to the detected position of the object 300.

[0060] Furthermore, in step S406, the imaging signal processing unit 112 may perform image recognition of the object 300, and the image recognition result may also be recorded as metadata in the image file. When combining multiple images, only images of the same object 300 may be combined. This prevents an error in which an image of one object 300 is mistakenly combined with an image of another object 300 when another object 300 enters the gate consecutively. [Example]

[0061] Next, Fig. 8 is a flowchart illustrating the processing flow of the gate system 200 in the second embodiment of the present invention. The operation of each step in Fig. 8 is performed by the computer inside the control unit 130 executing a computer program stored in memory. The functional block configuration of the gate system 200 in the second embodiment may be the same as that shown in FIG.

[0062] 8, when the gate system 200 starts to be used, in step S501, the object detection sensor 122 and the visible light camera 109 are powered on. This starts detecting whether or not an object 300 has entered the gate system 200, and also starts capturing an image of the object 300 in visible light using the visible light camera.

[0063] Next, in step S502, if it is determined that the object 300 has entered the gate system 200, the process proceeds to step S503; otherwise, step S502 is repeated. In step S503, the power sources of the imaging unit 110, the irradiation unit 120, and the distance measurement unit 123 are turned on, and imaging with terahertz waves is started.

[0064] In step S504, the distance between the object 300 and the imaging unit 110 and the irradiation unit 120 is measured using the distance measuring unit 123. In this embodiment, in order to keep the size of the object 300 or the first object constant in the first image signal, the shooting angle of the imaging unit 110 is changed depending on the distance between the object 300 and the imaging unit 110 and the irradiation unit 120.

[0065] That is, in step S505, the angle of view is determined from the distance between the imaging unit 110 and the irradiation unit 120. The angle of view can be determined by determining the distance between the imaging unit 110 and the object 300 and the imaging range of the imaging unit 110 at the distance between the imaging unit 110 and the object 300.

[0066] Next, in step S506, the angle of view of the optical system in imaging unit 110 is controlled to make the size of object 300 approximately the same. Then, in step S507, a still image is captured using terahertz waves at that angle of view using imaging unit 110 and irradiation unit 120. At this time, the focus of the optical system of the imaging unit may be adjusted according to the distance measured in step S404 so that an image that is always in focus can be obtained.

[0067] Furthermore, in step S508, the first image signals captured up to that point are combined to create a single combined image, which is displayed on the display unit 115. At this time, the image capture signal processing unit 112 performs image recognition to check for predetermined dangerous objects or prohibited items such as knives, and if a dangerous object or prohibited item is recognized, a warning is immediately displayed on the display unit 115. At this time, the warning may also be given by voice.

[0068] Next, in step S509, the distance to the object 300 is measured, for example, by a distance measurement unit, and if it is determined that the object 300 has exited the gate system 200, the process proceeds to step S510. Then, the power to the imaging unit 110, the irradiation unit 120, and the distance measurement unit 123 are turned off. If the answer is No in step S509, steps S504 to S508 are repeated to repeat image synthesis. Since the angle of view is adjusted during this process, the size of the object 300 is kept approximately constant. Therefore, the image recognition accuracy of the first object (for example, a dangerous object or a prohibited item) can be improved at an early stage, and a warning, etc., can be issued at an early stage. [Example]

[0069] FIG. 9 is a diagram illustrating a gate system 200 according to a third embodiment of the present invention. In this embodiment, a visible light camera 109 capable of controlling at least one of pan, tilt, and zoom is installed in a gate system 200 in which the imaging device 100 shown in Fig. 6 is installed. When a terahertz wave image (first image signal) is synthesized with a second image signal from the visible light camera 109, the control unit 130 performs zoom control (control of imaging magnification) of the optical system of the visible light camera 109.

[0070] This allows adjustment so that the size of the object 300 within the angle of view in the second image signal is uniform. Furthermore, by controlling at least one of panning and tilting using the control unit 130, the position of the object 300 as the second object in the second image signal is adjusted so that it is uniform at a predetermined position, such as the center of the screen.

[0071] As explained in the first and second embodiments, in imaging using terahertz waves, the imageable area of ​​the object 300 changes depending on the positional relationship between the object 300, the imaging unit 110, and the irradiation unit 120. Therefore, in the first and second embodiments, multiple terahertz wave images are synthesized to obtain an overall image, and the size of the object 300 is made uniform by enlarging or reducing the image signal through image processing, and the position is further adjusted through image processing before synthesis.

[0072] On the other hand, in this embodiment, before combining the second image signals obtained from the visible light camera 109, zoom control of the visible light camera 109 is used to make the size of the object 300 uniform. Furthermore, when combining the image obtained from the visible light camera 109 arranged in the gate system 200 with the terahertz wave image, the position of the object 300 is adjusted by pan / tilt control of the visible light camera 109 so that the position of the object 300 does not shift within the angle of view. [Example]

[0073] In the third embodiment, when taking multiple images, pan, tilt, and zoom controls are performed to adjust the size of the object 300 and align its position on the screen, but in the fourth embodiment, the size and position are adjusted by image processing.

[0074] To achieve this, when the terahertz wave image is captured, a visible light image of the object 300 is acquired by the visible light camera 109 in Fig. 9, and the terahertz wave image and the visible light image are combined. Then, the object 300 or the second object in the combined image is recognized, and the size of the object 300 or the second object is adjusted by image processing so that it has a predetermined size. Furthermore, the position of the object 300 or the second object is adjusted by image processing so that it is located, for example, in the center of the combined image, and the image is saved as an image file.

[0075] Each time a plurality of terahertz wave images are captured, similar image processing for combining, adjusting the size, and adjusting the position is performed and saved as an image file, and an image file suitable for combining is selected from the saved plurality of image files before combining them. By doing so, the size and position of the object 300 and the terahertz wave image are not distorted in the final composite image. Instead of adjusting the size and position of the target object 300 as described above, it is also possible to adjust the size and position of a predetermined object detected in a terahertz wave image, for example.

[0076] The present invention has been described in detail above based on its preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications are possible based on the gist of the present invention, and these modifications are not excluded from the scope of the present invention. Note that a computer program that realizes part or all of the control in this embodiment and the functions of the above-described embodiment may be supplied to an imaging device or the like via a network or various storage media. Then, a computer (or a CPU, MPU, or the like) in the imaging device or the like may read and execute the program. In this case, the program and the storage medium storing the program constitute the present invention. [Explanation of symbols]

[0077] 100: Imaging device 109: Visible light camera 110: Imaging unit 120: Irradiation unit 122: Object detection sensor 123: Distance measurement unit 200: Gate system 300: Object

Claims

1. an irradiation means for irradiating a target with terahertz waves; a first imaging means for imaging a reflected wave from the object irradiated with the terahertz wave by the irradiation means; an imaging signal processing means for processing an imaging signal obtained from the first imaging means to generate a first image signal and for image-recognizing a predetermined first object from the first image signal; an image processing means for synthesizing a plurality of the first image signals to generate a synthesized image; a control means for capturing images of the object a plurality of times using the first imaging means while the object is moving, generating a plurality of first image signals using the imaging signal processing means, and for generating a composite image by selecting and combining the plurality of first image signals using the image processing means, The control means adjusts at least one of the size and position of the first object in the first image signals, and then combines the first image signals obtained by imaging the object as a moving inspection target at different positions using the first imaging means.

2. 2. The imaging device according to claim 1, wherein the image processing means enlarges or reduces the first image signal to adjust the size of the first object.

3. 3. The imaging apparatus according to claim 1, wherein the image processing means performs image processing on the first image signal to adjust the position of the first target.

4. a second imaging means for imaging the object with visible light; the imaging signal processing means processes the imaging signal obtained from the second imaging means to generate a second image signal; 4. The imaging device according to claim 1, wherein the image processing means combines a plurality of the first image signals and the second image signals.

5. 5. The imaging device according to claim 4, wherein the imaging signal processing means performs image recognition of a predetermined second object from the second image signal.

6. 6. The imaging device according to claim 5, wherein the image processing means adjusts at least one of the size and position of the second object in the second image signal, and then combines the plurality of first image signals with the second image signal.

7. 7. The imaging device according to claim 6, wherein the image processing means enlarges or reduces the second image signal to adjust the size of the second object.

8. 8. The imaging apparatus according to claim 6, wherein the image processing means performs image processing on the second image signal to adjust the position of the second target.

9. the second imaging means includes an optical system; 7. The imaging apparatus according to claim 6, wherein the imaging magnification of the optical system is controlled to adjust the size of the second object.

10. 10. The imaging apparatus according to claim 9, wherein the control means controls panning or tilting of the optical system to adjust the position of the second object.

11. 10. The imaging device according to claim 9, wherein the control means enlarges or reduces the plurality of first image signals in accordance with the distance to the object, and combines the signals.

12. 10. The imaging device according to claim 9, wherein the control means records the image recognition result of the object in association with the first image signal.

13. an irradiation step of irradiating the object with terahertz waves; a first imaging step of imaging a reflected wave from the object irradiated with the terahertz wave in the irradiation step; an imaging signal processing step of processing the imaging signal obtained in the first imaging step to generate a first image signal and performing image recognition of a predetermined first object from the first image signal; an image processing step of capturing an image of the object a plurality of times in the first imaging step while the object is moving, generating a plurality of first image signals in the imaging signal processing step, and generating a composite image by selecting and combining the plurality of first image signals, The imaging method is characterized in that the image processing step images a moving object as an inspection target at different positions in the first imaging step, and the multiple first image signals obtained in the imaging signal processing step are synthesized after adjusting at least one of the size and position of the first object in the first image signals.

14. A computer program for causing a computer to function as the imaging signal processing means, the image processing means, and the control means of the imaging device according to any one of claims 1 to 12.

Images