JP2023055291A - camera system - Google Patents

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

The present invention relates to a camera system using terahertz waves.

Conventionally, in order to detect dangerous goods at airports, etc., terahertz waves, which are defined as electromagnetic waves having a frequency of 30 GHz or more and 30 THz or less, are irradiated to an object to be inspected, and the terahertz waves reflected by the object to be inspected are detected by a camera. Camera systems are known. Patent Literature 1 discloses a moving body scanner that irradiates a moving body as an inspection target with terahertz waves and specifies belongings using an image formed by the terahertz waves reflected from the moving body.

JP 2019-190951

In the mobile scanner disclosed in Patent Document 1, as the number of lights increases, power consumption increases and heat generation increases, resulting in an increase in the size of the heat dissipation mechanism and a reduction in life. Moreover, when the inspection object is a person, there are few places perpendicular to the incident light, so most of the intensity of the terahertz wave reflected from the inspection object is low.

An object of the present invention is to provide a camera system capable of appropriately detecting terahertz waves reflected from an inspection object while reducing the number of illuminations.

A camera system as one aspect of the present invention includes at least one illumination unit that irradiates an object to be inspected with terahertz waves, and a camera unit that acquires an image formed by the terahertz waves reflected by the object to be inspected. The first lighting unit includes a first direction orthogonal to the optical axis of the camera unit and lighting elements arranged in a two-dimensional manner along a second direction orthogonal to the first direction and a traveling direction of the inspection object, On the front side in the two directions, the number of lighting elements arranged relatively outward in the first direction is greater than the number of lighting elements arranged relatively inside in the first direction, and the number of lighting elements arranged relatively inside in the first direction is greater. On the side, the number of lighting elements arranged relatively outward in the first direction is less than the number of lighting elements arranged relatively inside in the first direction.

ADVANTAGE OF THE INVENTION According to this invention, the camera system which can detect appropriately the terahertz wave reflected from the test object can be provided, suppressing the number of illuminations.

1 is a block diagram of a camera system according to an embodiment of the invention; FIG. 1 is a schematic diagram of a camera system; FIG. 1 is a top view of a camera system; FIG. FIG. 4 is a diagram showing an image to be acquired; FIG. 4 is a schematic diagram of an illumination unit of Example 1. FIG. 4 is a diagram showing the arrangement of a plurality of lighting elements of Example 1. FIG. FIG. 10 is a diagram showing the arrangement of a plurality of lighting elements in Example 2; FIG. 11 is a diagram showing the arrangement of a plurality of lighting elements of Example 3; FIG. 11 is a diagram showing the arrangement of a plurality of lighting elements in Example 4;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same reference numerals are given to the same members, and overlapping descriptions are omitted.

FIG. 1 is a block diagram of a camera system 100 according to an embodiment of the invention. The camera system 100 irradiates an object to be inspected with terahertz waves, and inspects the surface or inside of the object to be inspected in a non-contact manner using an image formed by the terahertz waves reflected by the object to be inspected.

The camera system 100 has a control section 110 , an illumination control section 130 , an illumination section 131 , an imaging control section 140 , an imaging section (camera section) 141 , an imaging signal processing section 142 , and a display section 143 .

The control unit 110 controls the imaging control unit 140 and the lighting control unit 130 .

The illumination control section 130 controls the illumination section 131 . For example, the illumination control unit 130 can control the illumination intensity of the illumination unit 131, the illumination timing, and the like. The illumination unit 131 is an oscillator that generates terahertz waves, and irradiates the inspection object with the terahertz waves.

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

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. At that time, the imaging signal processing unit 142 may perform image processing such as noise removal and edge extraction. In addition, the imaging signal processing unit 142 may be configured to be able to detect an object in image data using an image recognition technique.

The display unit 143 displays image data processed by the imaging signal processing unit 142 . Also, the display unit 143 may display the result detected by the image recognition of the imaging signal processing unit 142 . For example, if a particular object is detected within the image data, the display unit 143 may display information only indicating that the detection has occurred.

FIG. 2 is a schematic diagram of a camera system 100, and a pedestrian as an inspection object 200 is inspected using the camera system 100 at an X-ray gate of an airport security station, an entrance/exit control gate of a building, or the like. showing the situation. FIG. 2A is a front view of the camera system 100. FIG. FIG. 2B is a side view of the camera system 100. FIG. In the following description, the X-axis direction (first direction) is a direction perpendicular to the optical axis of the imaging section 141 . The Y-axis direction (second direction) is orthogonal to the X-axis direction and is the traveling direction of the inspection object 200 . The Z-axis direction is a direction orthogonal to the X-axis direction and the Y-axis direction.

The lighting unit 131 is installed in the lower part of the passage. The imaging unit 141 is installed above the passage. Note that the illumination unit 131 may be installed above the passageway, and the imaging unit 141 may be installed below the passageway. Also, the lighting unit 131 and the imaging unit 141 may be installed on the side surface of the passage. Also, in FIG. 2, the number of imaging units 141 is one, but may be plural.

As shown in FIG. 2B, the illumination unit 131 irradiates a terahertz wave indicated by a light ray 220 to the inspection target 200 walking along the traveling direction 210 . An illumination area 221 is an area of the inspection object 200 illuminated by the illumination unit 131 . The imaging unit 141 acquires an image corresponding to the illumination area 221 formed by the terahertz wave indicated by the light ray 222 reflected by the inspection object 200 . Although the illumination area 221 is the upper half of the body in this embodiment, it may be the whole body or a part of the body.

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

FIG. 4 shows an image acquired when the subject 200 has a knife 410 and a dangerous object 420 concealed under their clothes. FIG. 4(a) shows an image acquired using a visible camera. FIG. 4B shows an image formed by terahertz waves. In the image of FIG. 4A, since the knife 410 and the dangerous object 420 are hidden under the clothes, it cannot be detected that the inspection target 200 has the knife 410 and the dangerous object 420. FIG. On the other hand, in the image of FIG. 4(b), the knife 410 and the dangerous object 420 have a high intensity, and it can be detected that the inspection target 200 is holding the knife 410 and the dangerous object 420. FIG.

As the number of lights increases, power consumption increases and heat generation increases, resulting in a larger heat dissipation mechanism and a shorter life. Therefore, in the camera system 100, it is preferable to reduce the number of illuminations. In each of the following examples, a method for arranging the plurality of lighting elements 132 will be described. In each embodiment, the area illuminated by the illumination unit 131 is the illumination area 221 in FIG. 2(a).

FIG. 5 is a schematic diagram of the illumination unit 131 of this embodiment. FIG. 5(a) is a schematic diagram when a plurality of lighting elements 132 are arranged in a rectangular shape. FIG. 5B is a schematic diagram of a case in which a plurality of lighting elements 132 are arranged according to the shape of the human body. FIGS. 5(c) and 5(d) are ray tracing simulations of images obtained when multiple illumination elements 132 are arranged as shown in FIGS. 5(a) and 5(b), respectively. Results (simulated images) are shown. As shown in FIGS. 5(c) and 5(d), the simulation images show the same subject. This is because the active method obtains the regular reflection component from the inspection target 200, but the regular reflection component does not enter the imaging unit 141 even if the illumination of the inspection target 200 that does not match the shape of the human body is reflected. It is believed that there is. Therefore, even if a plurality of lighting elements 132 are arranged as shown in FIG. 5(b), there is no problem in obtaining an image. When a plurality of lighting elements 132 are arranged as shown in FIG. 5(b), the number of lights can be reduced compared to the case where a plurality of lighting elements 132 are arranged as shown in FIG. 5(a). can.

FIG. 6 is a diagram showing an example of arrangement of the plurality of lighting elements 132 of this embodiment. On the minus side (front side) in the Y-axis direction, the number of lighting elements 132 arranged relatively outside in the X-axis direction is greater than the number of lighting elements 132 arranged relatively inside in the X-axis direction. configured to be Thereby, the lighting elements 132 are arranged in an arc shape to match the rounded shape of the human body. In addition, on the plus side (back side) in the Y-axis direction, the number of lighting elements 132 arranged outside in the X-axis direction is equal to the number of lighting elements 132 arranged inside in the X-axis direction in accordance with the shape of the human body. configured to be less than In addition, it is preferable that the lighting element 132 is not arranged outside in the X-axis direction. With the arrangement described above, the inspection object 200 can be imaged with a small number of illuminations.

FIG. 7 is a diagram showing an example of arrangement of the plurality of lighting elements 132 of this embodiment. The arrangement of the plurality of lighting elements 132 in this embodiment is the same as the arrangement described in the first embodiment. In this embodiment, the angle formed between the lighting element 132 positioned relatively outside in the X-axis direction and the Y-axis direction is the angle formed between the lighting element 132 positioned relatively inside in the X-axis direction and the Y-axis direction. configured to be larger than This makes it easier for the inspection object 200 to be illuminated.

FIG. 8 is a diagram showing an example of arrangement of the plurality of lighting elements 132 of this embodiment. On the minus side of the Y-axis direction, the arrangement density of the lighting elements 132 arranged relatively outside in the X-axis direction is higher than the arrangement density of the lighting elements 132 arranged relatively inside in the X-axis direction. configured to Also, on the positive side in the Y-axis direction, the arrangement density of the lighting elements 132 arranged outside in the X-axis direction is lower than the arrangement density of the lighting elements 132 arranged inside in the X-axis direction.

FIG. 9 is a diagram showing an example of arrangement of the plurality of lighting elements 132 of this embodiment. In this embodiment, a plurality of illumination units 131 of the first embodiment are arranged. As a result, imaging is possible even if the inspection target 200 moves.

Although 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.

100 camera system 131 lighting unit 132 lighting element 141 imaging unit (camera unit)
200 inspection object

Claims (5)

at least one illumination unit that irradiates a terahertz wave to an object to be inspected;
a camera unit for acquiring an image formed by the terahertz wave reflected by the inspection object;
The at least one illumination unit is arranged two-dimensionally along a first direction orthogonal to the optical axis of the camera unit and a second direction orthogonal to the first direction and a traveling direction of the inspection object. Equipped with a lighting element,
On the front side in the second direction, the number of the lighting elements arranged relatively outside in the first direction is greater than the number of the lighting elements arranged relatively inside in the first direction. ,
On the back side in the second direction, the number of the lighting elements arranged relatively outward in the first direction is smaller than the number of the lighting elements arranged relatively inside in the first direction. A camera system characterized by: The angle formed by the optical axis of the lighting element arranged relatively outside in the first direction and the second direction is the optical axis of the lighting element arranged relatively inside in the first direction. 2. The camera system of claim 1, wherein the angle is greater than the angle formed with the second direction. On the front side in the second direction, the arrangement density of the lighting elements arranged relatively outside in the first direction is higher than the arrangement density of the lighting elements arranged relatively inside in the first direction. is also high,
On the far side in the second direction, the arrangement density of the lighting elements arranged relatively outside in the first direction is higher than the arrangement density of the lighting elements arranged relatively inside in the first direction. 3. Camera system according to claim 1 or 2, characterized in that . The at least one lighting unit comprises a plurality of lighting units,
4. The camera system according to any one of claims 1 to 3, wherein the plurality of lighting units are arranged along the second direction. 5. The camera system according to any one of claims 1 to 4, wherein on the far side in the second direction the lighting elements are not arranged relatively outside in the first direction.

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