Camera System

Abstract

To provide a camera system that can appropriately detect a terahertz wave reflected on a test object while reducing the number of illuminations.SOLUTION: A camera system has at least one illumination unit that irradiates a test object with a terahertz wave, and a camera unit that acquires an image formed by the terahertz wave reflected on the test object. At least one illumination unit includes illumination elements that are arranged in a two-dimensional shape along a first direction orthogonal to an optical axis of the camera unit and a second direction orthogonal to the first direction and being a direction of travel of the test object. On a front side in the second direction, the number of the illumination elements arranged relatively outside in the first direction is larger than the number of the illumination elements arranged relatively inside in the first direction, and on a back side in the second direction, the number of the illumination elements arranged relatively outside in the first direction is smaller than the number of the illumination elements arranged relatively inside in the first direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a camera system that utilizes terahertz waves. [Background technology]

[0002] Conventionally, in order to detect dangerous objects at airports etc., a camera system is known in which terahertz waves, which are defined as electromagnetic waves having a frequency of 30 GHz or more and 30 THz or less, are irradiated onto an object to be inspected, and the terahertz waves reflected from the object are detected by a camera. Patent Document 1 discloses a mobile object scanner that irradiates terahertz waves onto a moving object as an object to be inspected, and identifies belongings using an image formed by the terahertz waves reflected from the moving object. [Prior art documents] [Patent documents]

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

[0004] In the mobile scanner of Patent Document 1, increasing the number of lights increases power consumption and heat generation, which results in an increase in the size of the heat dissipation mechanism and a shortened lifespan. Also, when the object to be inspected is a person, there are few points where the incident light is perpendicular, so the intensity of most of the terahertz waves reflected from the object to be inspected is low.

[0005] An object of the present invention is to provide a camera system that can appropriately detect terahertz waves reflected from an object to be inspected while reducing the number of lights required. [Means for solving the problem]

[0006] A camera system according to one aspect of the present invention includes at least one illumination unit that irradiates an inspection object with terahertz waves, and a camera unit that acquires an image formed by the terahertz waves reflected by the inspection object, wherein the at least one illumination unit includes illumination elements that are two-dimensionally arranged along a first direction that is orthogonal to an optical axis of the camera unit and a second direction that is orthogonal to the first direction and is a traveling direction of the inspection object; The number of the illumination elements is reduced on the front side and the back side in the second direction of the illumination unit, On the near side in the second direction, the number of lighting elements arranged relatively outward in the first direction is greater than the number of lighting elements arranged relatively inward in the first direction, and on the far side in the second direction, the number of lighting elements arranged relatively outward in the first direction is less than the number of lighting elements arranged relatively inward in the first direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a camera system that can appropriately detect terahertz waves reflected from an object to be inspected while reducing the number of lighting devices. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram of a camera system according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram of a camera system. [Figure 3] FIG. 2 is a top view of the camera system. [Figure 4] FIG. 10 is a diagram showing an image to be acquired. [Figure 5] FIG. 2 is a schematic diagram of an illumination unit according to the first embodiment. [Figure 6] FIG. 2 is a diagram showing the arrangement of a plurality of lighting elements according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing the arrangement of a plurality of lighting elements according to a second embodiment. [Figure 8] FIG. 10 is a diagram showing the arrangement of a plurality of lighting elements according to a third embodiment. [Figure 9] FIG. 10 is a diagram showing the arrangement of a plurality of lighting elements in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same components, and redundant explanations will be omitted.

[0010] 1 is a block diagram of a camera system 100 according to an embodiment of the present invention. The camera system 100 irradiates an inspection object with terahertz waves and inspects the surface or interior of the inspection object in a non-contact manner using an image formed by the terahertz waves reflected from the inspection object.

[0011] The camera system 100 includes a control unit 110, an illumination control unit 130, an illumination unit 131, an imaging control unit 140, an imaging unit (camera unit) 141, an imaging signal processing unit 142, and a display unit 143.

[0012] The control unit 110 controls the imaging control unit 140 and the illumination control unit 130 .

[0013] The illumination control unit 130 controls the illumination unit 131. For example, the illumination control unit 130 can control the illumination intensity and timing of the illumination unit 131. The illumination unit 131 is an oscillator that generates terahertz waves, and irradiates the object to be inspected with the terahertz waves.

[0014] The imaging control unit 140 controls the imaging unit 141. The imaging unit 141 is an imaging sensor that has high sensitivity to terahertz waves, and acquires an image (terahertz image) formed by terahertz waves reflected from an inspection object. The imaging unit 141 also controls the exposure time. The imaging unit 141 may also be able to adjust the depth of field and exposure time by adjusting the F-number and shutter speed.

[0015] The imaging signal processing unit 142 processes the imaging signal from the imaging unit 141. The imaging signal processing unit 142 converts the imaging signal into an image signal. In this process, the imaging signal processing unit 142 may perform image processing such as noise removal and edge extraction. The imaging signal processing unit 142 may also be configured to be able to detect objects in image data using image recognition technology.

[0016] The display unit 143 displays the image data processed by the imaging signal processing unit 142. The display unit 143 may also display the results of detection by the image recognition of the imaging signal processing unit 142. For example, when a specific object is detected in the image data, the display unit 143 may display information indicating only that the detection has been performed.

[0017] FIG. 2 is a schematic diagram of the camera system 100, showing a situation in which the camera system 100 is used to inspect a pedestrian as an inspection target 200 at an X-ray gate at an airport security station or an entrance / exit control gate at a building. FIG. 2(a) is a front view of the camera system 100. FIG. 2(b) is a side view of the camera system 100. In the following description, the X-axis direction (first direction) is a direction perpendicular to the optical axis of the imaging unit 141. The Y-axis direction (second direction) is perpendicular to the X-axis direction and is the traveling direction of the inspection target 200. The Z-axis direction is a direction perpendicular to the X-axis and Y-axis directions.

[0018] The lighting unit 131 is installed at the bottom of the passage. The imaging unit 141 is installed at the top of the passage. It is also possible to install the lighting unit 131 at the top of the passage and the imaging unit 141 at the bottom of the passage. It is also possible to install the lighting unit 131 and the imaging unit 141 on the side of the passage. Also, although there is one imaging unit 141 in FIG. 2, there may be multiple imaging units.

[0019] As shown in FIG. 2(b), the illumination unit 131 irradiates the inspection object 200 walking along the traveling direction 210 with terahertz waves indicated by light beam 220. An illumination area 221 is an area of ​​the inspection object 200 irradiated by the illumination unit 131. The imaging unit 141 acquires an image corresponding to the illumination area 221 formed by the terahertz waves indicated by light beam 222 reflected by the inspection object 200. Note that in this embodiment, the illumination area 221 is the upper body, but it may be the whole body or a part of the body.

[0020] 3 is a top view of the camera system 100. The illumination unit 131 includes a plurality of illumination elements 132 arranged two-dimensionally on the XY plane. The plurality of illumination elements 132 can be independently turned on / off and their intensity can be adjusted.

[0021] FIG. 4 shows images acquired when the inspection target 200 is hiding a knife 410 and a dangerous object 420 under his clothes. FIG. 4(a) shows an image acquired using a visible light camera. FIG. 4(b) shows an image formed using terahertz waves. In the image of FIG. 4(a), the knife 410 and the dangerous object 420 are hidden under the clothes, so it is not possible to detect that the inspection target 200 is holding the knife 410 and the dangerous object 420. On the other hand, in the image of FIG. 4(b), the intensity is high in the areas of the knife 410 and the dangerous object 420, making it possible to detect that the inspection target 200 is holding the knife 410 and the dangerous object 420.

[0022] Increasing the number of lighting devices increases power consumption and heat generation, which in turn leads to a larger heat dissipation mechanism and a shorter lifespan. For this reason, it is preferable to reduce the number of lighting devices in the camera system 100. In the following embodiments, a method for arranging multiple lighting elements 132 will be described. In each embodiment, the area illuminated by the lighting unit 131 is the lighting area 221 in FIG. 2(a). [Example]

[0023] FIG. 5 is a schematic diagram of the illumination unit 131 of this embodiment. FIG. 5(a) is a schematic diagram of a rectangular arrangement of multiple illumination elements 132. FIG. 5(b) is a schematic diagram of a human body-shaped arrangement of multiple illumination elements 132. FIG. 5(c) and FIG. 5(d) show ray-tracing simulation results (simulation images) of images acquired when multiple illumination elements 132 are arranged as shown in FIG. 5(a) and FIG. 5(b), respectively. As shown in FIG. 5(c) and FIG. 5(d), the subject appears the same in the simulation images. This is thought to be because the active method acquires specular reflection components from the inspection object 200, but when illumination at a location that does not match the shape of the human body is reflected by the inspection object 200, the specular reflection components do not enter the imaging unit 141. Therefore, there is no problem with image acquisition even when multiple illumination elements 132 are arranged as shown in FIG. 5(b). When a plurality of lighting elements 132 are arranged as shown in FIG. 5(b), the number of lights can be reduced compared to when a plurality of lighting elements 132 are arranged as shown in FIG. 5(a).

[0024] FIG. 6 is a diagram showing an example of the arrangement of a plurality of illumination elements 132 in this embodiment. On the negative side (near side) in the Y-axis direction, the number of illumination elements 132 arranged relatively outward in the X-axis direction is configured to be greater than the number of illumination elements 132 arranged relatively inward in the X-axis direction. As a result, the illumination elements 132 are arranged in an arc shape to match the rounded shape of the human body. Furthermore, on the positive side (deep side) in the Y-axis direction, the number of illumination elements 132 arranged outward in the X-axis direction is configured to be less than the number of illumination elements 132 arranged inward in the X-axis direction, in accordance with the shape of the human body. Note that it is preferable that the illumination elements 132 are not arranged outward in the X-axis direction. With the arrangement described above, it is possible to image the inspection object 200 with a small number of illuminations. [Example]

[0025] 7 is a diagram showing an example of the arrangement of the plurality of illumination elements 132 in this embodiment. The arrangement of the plurality of illumination elements 132 in this embodiment is the same as the arrangement described in embodiment 1. In this embodiment, the angle formed between the illumination elements 132 located relatively outward in the X-axis direction and the Y-axis direction is larger than the angle formed between the illumination elements 132 located relatively inward in the X-axis direction and the Y-axis direction. This makes it easier for the illumination to hit the inspection object 200. [Example]

[0026] 8 is a diagram showing an example of the arrangement of a plurality of lighting elements 132 in this embodiment. On the negative side of the Y axis direction, the arrangement density of the lighting elements 132 arranged relatively outward in the X axis direction is configured to be higher than the arrangement density of the lighting elements 132 arranged relatively inward in the X axis direction. On the positive side of the Y axis direction, the arrangement density of the lighting elements 132 arranged relatively outward in the X axis direction is configured to be lower than the arrangement density of the lighting elements 132 arranged relatively inward in the X axis direction. [Example]

[0027] 9 is a diagram showing an example of the arrangement of a plurality of illumination elements 132 in this embodiment. In this embodiment, a plurality of illumination units 131 of embodiment 1 are arranged. This allows imaging of the inspection object 200 even if it moves.

[0028] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0029] 100 Camera System 131 Lighting Department 132 lighting elements 141 Imaging unit (camera unit) 200 inspection targets

Claims

1. at least one illumination unit that irradiates the inspection object with terahertz waves; a camera unit for acquiring an image formed by the terahertz wave reflected from the inspection object, the at least one illumination unit includes illumination elements two-dimensionally arranged along a first direction orthogonal to an optical axis of the camera unit and a second direction orthogonal to the first direction and being a traveling direction of the inspection object; the number of the lighting elements arranged in the lighting unit is reduced on the front side and the back side in the second direction, On the near side in the second direction, the number of the lighting elements arranged relatively outward in the first direction is greater than the number of the lighting elements arranged relatively inward in the first direction, A camera system characterized in that, at the back side in the second direction, the number of lighting elements arranged relatively outward in the first direction is smaller than the number of lighting elements arranged relatively inward in the first direction.

2. 2. The camera system of claim 1, wherein the angle between the optical axis of the lighting element arranged relatively outward in the first direction and the second direction is larger than the angle between the optical axis of the lighting element arranged relatively inward in the first direction and the second direction.

3. On the near side in the second direction, the arrangement density of the lighting elements arranged relatively outward in the first direction is higher than the arrangement density of the lighting elements arranged relatively inward in the first direction, 3. The camera system of claim 1, wherein the arrangement density of the lighting elements arranged relatively outward in the first direction is lower at the rear side in the second direction than the arrangement density of the lighting elements arranged relatively inward in the first direction.

4. the at least one illumination unit comprises a plurality of illumination units; The camera system according to claim 1 , wherein the plurality of illumination units are arranged along the second direction.

5. 5. The camera system according to claim 1, wherein the illumination elements are not arranged relatively farther outward in the first direction than the illumination elements in the second direction.

6. A camera system described in any one of claims 1 to 5, characterized in that the arrangement density of the lighting elements arranged relatively inward in the first direction gradually increases from the front side to the back side in the second direction.

7. A camera system described in any one of claims 1 to 6, characterized in that in the lighting section, the lighting elements are arranged side by side across the floor surface from the object to be inspected.

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