JP7614899B2 - Inspection Equipment - Google Patents

Description

The present invention relates to technology for an inspection device that inspects people's belongings using electromagnetic waves.

As a scanner for inspecting the inside of an object, for example, a body scanner for carrying out body checks at airports etc. is known (for example, see Patent Document 1).

Patent document 2 discloses a mobile scanner that detects the position of a moving object (mobile body) such as a pedestrian and switches the propagation direction of terahertz waves depending on the detected position.

JP 2015-36680 A JP 2019-190951 A

Methods of imaging objects using electromagnetic waves include active imaging, in which electromagnetic waves are irradiated onto an object and the transmitted or reflected waves are detected to create an image, and passive imaging, in which electromagnetic waves emitted from the object itself are detected to create an image.

For example, terahertz waves are electromagnetic waves with a frequency of 100 GHz or more but less than 10 THz. These terahertz waves are also used in the active imaging mentioned above, but because they are emitted in minute amounts from the human body and belongings, they are also used in the passive imaging type walk-through possession inspection device mentioned above, which uses the difference in the amount of radiation to detect concealed possessions.

To receive the weak terahertz waves emitted from an object, the receiving system needs to be compatible with a wide bandwidth. However, lenses have chromatic aberration and are therefore not suitable for broadband applications. Furthermore, if one were to attempt to collect the electromagnetic waves emitted from a person's entire body using a single parabolic mirror, a considerable depth would be required, making the device larger and making it difficult to save space. The same is true for active imaging.

One of the objectives of the present invention is to make the size of an inspection device that inspects a person's belongings based on collected electromagnetic waves smaller than would be possible without the composite mirror of the present invention.

In order to solve the above-mentioned problems, the present invention provides a method for arranging a plurality of concave mirrors with different focal lengths so that the optical axes and the foci overlap, and a method for arranging the concave mirrors with different focal lengths so that the optical axes and the foci overlap, the method being expressed using constants p and c1 and an independent variable x indicating the distance from the optical axis.
According to a first aspect of the present invention, there is provided an inspection device for inspecting a person's possessions based on electromagnetic waves collected by a composite mirror having a curved surface rotated around the optical axis, the functional curve being :

The inspection device of the first aspect can be made smaller than a device that does not use the composite mirror of the present invention and inspects people's belongings based on collected electromagnetic waves.

In the inspection device of the first aspect, a configuration in which the composite mirror is disposed so as not to block the line of movement of the person may be adopted as a second aspect.

According to the inspection device of the second aspect, the composite mirror does not impede the movement of people.

In the inspection apparatus according to the first or second aspect, a configuration in which the composite mirror has no gap when viewed from the focal point may be adopted as a third aspect.

According to the inspection device of the third aspect, even if the multiple concave mirrors constituting the composite mirror are spaced apart from each other, the reflected light beams that reach the focal point are continuous.

In the inspection device according to any one of the first to third aspects, a configuration in which the electromagnetic waves collected by the composite mirror are guided to a detector by an optical system arranged at the focal point may be adopted as a fourth aspect.

According to the inspection apparatus of the fourth aspect, the optical system guides the electromagnetic wave from the focus to the detector.

In the inspection apparatus of the fourth aspect, a configuration in which the optical system is a polygon mirror may be adopted as a fifth aspect.

According to the inspection device of the fifth aspect, a wide range can be inspected by rotating the optical system, which is a polygon mirror, to scan the inspection object.

FIG. 2 is a plan view showing an example of an inspection system 9 according to an embodiment of the present invention as seen from above. FIG. 4 is a conceptual diagram illustrating the height direction of the inspection device 1. FIG. 2 is a diagram for explaining a parabolic mirror. FIG. 2 is a diagram showing an example of a composite mirror 11 housed in the inspection device 1. 1 is a diagram showing an example of how the composite mirror 11 inspects electromagnetic waves emitted from an inspection target having a length Lz; 3A and 3B are diagrams showing examples of multiple concave mirrors that make up the composite mirror 11. FIG. 2 is a diagram showing an example of an inspection device 1 using a polygon mirror in an optical system 12. FIG. 2 is a diagram showing an example of a composite mirror 11 with no gap when viewed from a focal point P. 4 is a diagram showing an example of the shapes of multiple concave mirrors M expressed by one function.

<Embodiment>
<Configuration of the inspection device>
Hereinafter, in the figures, the space in which each component is arranged is represented as an XYZ right-handed coordinate space, or an xyz right-handed coordinate space. Among the coordinate symbols shown in the figures, a symbol with a dot in a circle represents an arrow pointing from the back of the paper to the front, and a symbol with two intersecting lines in a circle represents an arrow pointing from the front of the paper to the back. The direction along the x-axis in space is called the x-axis direction. Among the x-axis directions, the direction in which the x-component increases is called the +x direction, and the direction in which the x-component decreases is called the -x direction. The y, z, and X, Y, and Z components are defined in the same way as the x-component.

Figure 1 is a plan view showing an example of an inspection system 9 according to an embodiment of the present invention, seen from above. The inspection system 9 is a system for inspecting belongings of a person Q walking along an aisle, and a total of four inspection devices 1 are placed, two on each side of the aisle in positions that do not block the aisle. This aisle has a width W that extends in the Y-axis direction in an XYZ right-handed coordinate space, and includes the movement path of person Q when walking. Since none of the four inspection devices 1 are placed in positions that do not block the aisle, they do not block the movement path of person Q. Note that in Figure 1, the -Z direction is downward, that is, the direction of gravity, and the X-axis direction is the direction of the width of the aisle.

The four inspection devices 1 each receive (or receive) electromagnetic waves such as terahertz waves emitted in direction D from person Q and his/her belongings. As person Q walks (moves) in the +Y direction, the four inspection devices 1 scan person Q and his/her belongings in the Y-axis direction and the X-axis direction (i.e., the horizontal direction). The four inspection devices 1 also scan person Q and his/her belongings in the Z-axis direction.

Figure 2 is a conceptual diagram explaining the height direction of the inspection device 1. The possessions carried by person Q are, for example, in the range from above the knees to below the neck, as indicated by the diagonal lines in Figure 2. Therefore, the inspection device 1 must inspect the range along the Z axis from the position H1 of the knees of person Q walking on the floor surface G with the passageway described above to the position H2 of the neck. The length Lz of this range along the Z axis is, for example, 1200 millimeters.

Figure 3 is a diagram for explaining a parabolic mirror. A parabola passing through the origin O is drawn on the xy plane shown in Figure 3. This parabola is a curve connecting (x, y) when the dependent variable y is expressed as a quadratic function of the independent variable x. Here, the focus P is placed on the y axis, and its y component is p. In this case, the dependent variable y is expressed by the following equation (1).

ｙ軸を中心にして、この放物線を回転して得られる曲面は、放物面である。この放物面の凹部が鏡になった部材が放物面鏡である。上述した電磁波を受ける方向Ｄが－ｙ方向になるようにこの放物面鏡を配置すると、方向Ｄに放射される平行光は、いずれも焦点Ｐに集められる。

The curved surface obtained by rotating this parabola around the y-axis is a paraboloid. A component in which the concave portion of this paraboloid is a mirror is a parabolic mirror. If this parabolic mirror is positioned so that the direction D in which it receives the electromagnetic waves described above is the -y direction, all of the parallel light emitted in direction D will be focused at a focal point P.

When the range of the incident angle of the electromagnetic waves received at the focal point P by the parabolic mirror exceeds two right angles, i.e., 2π radians, the incident lights will face each other, making it difficult to convert them into collimated light (parallel light) by the optical system and guide them to the detector. Therefore, generally, neither of the y components of the end points E1 and E2 of this parabolic mirror exceeds p, which is the y component of the focal point P. And, for example, if the y components of the end points E1 and E2 are the same as p, which is the y component of the focal point P, then the distance from end point E1 to end point E2 is 4p.

Therefore, when the above-mentioned length Lz is to be inspected with a single parabolic mirror, its depth is Lz/4. When the above-mentioned length Lz is 1200 millimeters, the depth of the parabolic mirror is 300 millimeters. In other words, when the inspection target is, for example, a height of 1200 millimeters with a single parabolic mirror, the inspection device 1 needs to be large enough to accommodate a parabolic mirror with a depth direction of 300 millimeters.

<Configuration of the composite mirror>
Fig. 4 is a diagram showing an example of a composite mirror 11 housed in the inspection device 1. Fig. 5 is a diagram showing an example of the composite mirror 11 inspecting electromagnetic waves emitted from an inspection target having a length Lz. As described above, none of the inspection devices 1 blocks the movement line of the person Q, and the composite mirror 11 is housed in the inspection device 1. Therefore, none of the composite mirrors 11 shown in Figs. 4 and 5 block the movement line of the person Q.

Figure 4 shows the inside of the inspection device 1 viewed in the -Z direction. The xyz right-handed coordinate space is defined so that the +x direction coincides with the +Z direction, and the -y direction coincides with the direction D in which electromagnetic waves are received. The inspection device 1 shown in Figure 4 has a composite mirror 11, an optical system 12, and a detector 13.

The optical axis I of the composite mirror 11 extends in a direction parallel to the direction D. An optical system 12 is disposed at a focal point P on the optical axis I. This optical system 12 is, for example, a parabolic mirror, and adjusts the electromagnetic waves collected by the composite mirror 11 so that their directions of travel are parallel, and guides them to a detector 13 disposed on the optical axis I. In other words, the inspection device 1 having this optical system 12 is an example of an inspection device that guides the electromagnetic waves collected by the composite mirror to a detector by an optical system disposed at the focal point.

As shown in Figure 5, the thickness of the composite mirror 11 in the y-axis direction is less than one-fourth of the length Lz. This is because the composite mirror 11 is not a single parabolic mirror, but is formed by arranging multiple concave mirrors with different focal lengths so that their optical axes I and focal points P overlap.

<Detailed configuration of the composite mirror>
Fig. 6 is a diagram showing an example of multiple concave mirrors that make up the composite mirror 11. Fig. 6 shows a cross section of the composite mirror 11, which is a rotating body with the y-axis as its center of rotation, cut along an xy plane including the y-axis. The y-axis coincides with the optical axis I of the composite mirror 11.

This composite mirror 11 has a plurality of concave mirrors M ₀ , M ₁ , . . . , M _i , M _i+1 , . . . (hereinafter, when there is no need to distinguish between these, they will simply be referred to as concave mirror M).

The subscript i of each of the multiple concave mirrors M is an integer starting from 0, and when the subscript i=0, the concave mirror _M0 includes the origin O. The larger the subscript i, the farther the concave mirror M is from the y-axis.

The curves of the concave mirrors _M0 , _M1 , ..., _Mi , Mi ₊₁ , ... passing through the xy plane are each expressed as functions of the independent variable x, _f0 (x), _f1 (x), ..., _fi (x), _fi+1 (x), .... All of these functions shown in Fig. 6 are parabolas having a common optical axis I and focal point P. In other words, the multiple concave mirrors M constituting the composite mirror 11 shown in Fig. 6 are curved mirrors obtained by rotating the above-mentioned parabolas around the y-axis, that is, parabolic mirrors.

In general, y= _fi (x) is a parabola whose y coordinate on the y axis is _yi ( _yi ≦0) and whose focus is P(0,p), and is therefore expressed by the following formula (2), where _y0 =0 and i=0, 1, 2,... (integers starting from 0).

図６に示す凹面鏡Ｍは、いずれも厚みｔ（ただし、ｔ＜ｐ）を超えないように切り取られている。つまり、凹面鏡Ｍのｙ座標は０以上、かつ、ｔ以下である。凹面鏡Ｍ₀は原点Ｏで、それ以外の凹面鏡Ｍ_i（ｉ≧１）は、それぞれの内周で、いずれもｘ軸と接している。

6 is cut so that the thickness does not exceed t (where t<p). In other words, the y coordinate of the concave mirror M is equal to or greater than 0 and equal to or less than t. The concave mirror _M0 is at the origin O, and the other concave mirrors M _i (i≧1) are all in contact with the x-axis at their respective inner peripheries.

In addition, the outer periphery of each of the concave mirrors M is tangent to the line indicated by y = t. The x coordinate of the outer periphery of each of the multiple concave mirrors M _i (i ≥ 0) shown in Fig. 6 coincides with the x coordinate of the inner periphery of the adjacent concave mirror M _i+1 on the outside. In other words, the composite mirror 11 formed by these multiple concave mirrors M has no gaps when viewed from the y-axis direction.

Here, the x-coordinate of point _ai where y = _fi (x) shown in equation (2) touches the line shown by y = t is defined as _xi ( _xi > 0). A perpendicular line drawn from point _ai to the x-axis intersects with the x-axis at point _bi+1 . This point _bi+1 is the point where y = fi ₊₁ (x) intersects with the x-axis.

Of the multiple concave mirrors M shown in FIG. 6, concave mirror M ₀ has no inner periphery, and the other concave mirrors M _i (i≧1) have inner peripheries with y coordinates of 0.

As described above, y=f _i (x) passes through point a _i (x _i , t), so substituting this into equation (2) and expressing x _i in terms of p, y _i , t gives the following equation (3).

また、上述したとおり、ｙ＝ｆ_i+1（ｘ）は、点ｂ_i+1（ｘ_i，０）を通り、焦点Ｐ（０，ｐ）を有する。点ｂ_i+1（ｘ_i，０）と、焦点Ｐ（０，ｐ）との距離は、√（ｘ_i ²＋ｐ²）である。それゆえ、ｙ＝ｆ_i+1（ｘ）における準線は次の式（４）で示される。

As described above, y = f _i+1 (x) passes through point b _i+1 (x _i , 0) and has a focal point P(0, p). The distance between point b _i+1 (x _i , 0) and focal point P(0, p) is √(x _i ² +p ² ). Therefore, the directrix at y = f _i+1 (x) is expressed by the following equation (4).

この準線のｙ座標と、焦点Ｐのｙ座標との中点が、ｙ＝ｆ_i+1（ｘ）とｙ軸とが交差する点のｙ座標であるｙ_i+1に等しいから、ｙ_i+1は以下の式（５）で示される。

Since the midpoint between the y coordinate of this directrix and the y coordinate of the focus P is equal to y _i+1 , which is the y coordinate of the point where y = f _i+1 (x) intersects with the y axis, y _i+1 is expressed by the following equation (5).

この式（５）に式（３）を適用すると、ｙ_iについての漸化式である次の式（６）が得られる。

By applying equation (3) to equation (5), we obtain the following equation (6), which is a recurrence formula for y _i .

上述した通り、ｙ₀＝０を式（６）に代入することにより、ｙ₀、ｙ₁、…、ｙ_i、ｙ_i+1、…が得られる。そして、これらを式（２）に代入することにより、凹面鏡Ｍを示す関数ｆ₀（ｘ）、ｆ₁（ｘ）、…、ｆ_i（ｘ）、ｆ_i+1（ｘ）、…がそれぞれ定まる。これら複数の凹面鏡Ｍは、光軸Ｉに沿って－ｙ方向に進む電磁波を反射して焦点Ｐに集める。

As described above, by substituting y ₀ =0 into equation (6), we obtain y ₀ , y ₁ , ..., y _i , y _i+1 , .... Then, by substituting these into equation (2), functions f ₀ (x), f ₁ (x), ..., f _i (x), f _i+1 (x), ... representing the concave mirror M are determined. These multiple concave mirrors M reflect electromagnetic waves traveling in the -y direction along the optical axis I and collect them at the focal point P.

As explained above, the four inspection devices 1 provided in the inspection system 9 have a composite mirror 11 in which multiple concave mirrors M with different focal lengths are arranged so that their optical axes I and focal points P overlap. In the example shown in FIG. 6, this composite mirror 11 has a thickness t along the optical axis I that is thinner than p, but when it receives electromagnetic waves parallel to the optical axis I, it can focus them at the focal point P regardless of their x coordinate. Therefore, the inspection device 1 according to the present invention is smaller than one that does not use the composite mirror 11.

The configuration, shape, size, and layout relationship described in the above embodiments are merely shown in a schematic manner to enable the present invention to be understood and implemented. Therefore, the present invention is not limited to the described embodiments, and can be modified in various forms without departing from the scope of the technical ideas set forth in the claims.

<Modification>
The above is a description of the embodiment, but the contents of this embodiment may be modified as follows. In addition, the following modifications may be combined.

＜1＞
In the above-described embodiment, the optical system 12 is a parabolic mirror that collimates the electromagnetic waves collected by the composite mirror 11 and guides them to the detector 13, but other configurations are also possible. For example, the optical system 12 may be a polygon mirror.

Figure 7 is a diagram showing an example of an inspection device 1 that uses a polygon mirror in the optical system 12. The optical system 12 shown in Figure 7 is, for example, a pyramidal polygon mirror, which rotates around axis J to scan the composite mirror 11 in the Z-axis direction (x-axis direction). The electromagnetic waves reflected by the composite mirror 11 are further reflected by the optical system 12, and then further reflected by the parabolic mirror 14 and guided to the detector 13.

＜2＞
In the above-described embodiment, the composite mirror 11 is configured so as to have no gaps when viewed from the y-axis direction, but it is sufficient that there are no gaps when viewed from the focal point P.

Figure 8 is a diagram showing an example of a composite mirror 11 with no gaps when viewed from focal point P. In the composite mirror 11 shown in Figure 8, the point where a straight line extending from focal point P to a point on the outer periphery of concave mirror M intersects with the x-axis in the xy plane is a point on the inner periphery of concave mirror M located outside of that concave mirror M. Even with this configuration, electromagnetic waves traveling in the -y direction are reflected by multiple concave mirrors M and collected at focal point P. And because there are no gaps in composite mirror 11 when viewed from focal point P, the collected electromagnetic waves do not disperse.

＜3＞
In the above-described embodiment, the curved surface shapes of the multiple concave mirrors M are determined by different xy plane functions f ₀ (x), f ₁ (x), ..., f _i (x), f _i+1 (x), ..., but they may also be determined by a common function f(x).

Figure 9 is a diagram showing an example of the shape of multiple concave mirrors M represented by one function. The multiple concave mirrors M shown in Figure 9 have a shape obtained by cutting a single function f(x) along the y-axis direction at intervals of t. These multiple concave mirrors M are all arranged in a parallel translation such that their bottom ends are in contact with the x-axis.

In this case, each of the multiple concave mirrors M reflects electromagnetic waves incident in the -y direction on its inner circumference and directs them to a focal point P(0,p), and also reflects them on its outer circumference and directs them to a point Pt(0,p+t).

For example, on the composite mirror 11, a point with an x-coordinate of x _i exists on the outer circumference of the concave mirror M _i and on the inner circumference of the concave mirror M _i+1 . The inclination of these points on each concave mirror M coincides with the inclination of the tangent T at the point with the x-coordinate of x _i on the above-mentioned y = f(x). Therefore, electromagnetic waves incident in the -y direction at these points are reflected in the direction reflected by a plane mirror arranged along the tangent T.

The normal line N is a line perpendicular to the tangent line T at the point where the x-coordinate is x _i . The incident angle and the reflection angle shown in FIG. 9 are equal, and both are angles Φ. The complementary angle of twice the angle Φ is the angle θ between the x-axis and the above-mentioned reflection direction. Therefore, the relationship between the angles Φ and θ is expressed by the following formula (7).

また、角度θは、ｐ，ｘ_iにより以下の式（８）で表される。

Moreover, the angle θ is expressed by the following equation (8) using p and x _i .

上述したｘ_iは全てのｘ（ｘ≧０）で成り立つ。また、上述した法線Ｎの傾きは－ｔａｎ（θ＋Φ）である。法線Ｎと接線Ｔとは直交し、接線Ｔの傾きは上述した関数ｆ（ｘ）の１次微分に等しい。したがって、この１次微分は、還元公式により以下の式（９）で表される。

The above-mentioned x _i holds true for all x (x≧0). The gradient of the above-mentioned normal line N is -tan(θ+Φ). The normal line N and the tangent line T are perpendicular to each other, and the gradient of the tangent line T is equal to the first derivative of the above-mentioned function f(x). Therefore, this first derivative is expressed by the following equation (9) using the reduction formula.

この式（９）に式（７）、式（８）を適用し、ｘ_iをｘに置き換えると、以下の式（１１０）で表される常微分方程式が得られる。

By applying equations (7) and (8) to equation (9) and replacing x _i with x, the ordinary differential equation expressed by equation (110) below is obtained.

この式（１０）を、ｘについて積分すると、以下の式（１１）で表される通り、微分方程式の解が得られる。なお、式（１１）におけるｃ₁は積分定数である。

By integrating this equation (10) with respect to x, a solution to the differential equation is obtained as shown in the following equation (11): _c1 in equation (11) is an integral constant.

この式（１１）に対して、上述した点を通ることによる境界条件を満たすように積分定数ｃ₁を決めると関数ｆ（ｘ）が定まる。

For this equation (11), when the integral constant _c1 is determined so as to satisfy the boundary condition by passing through the above-mentioned points, the function f(x) is determined.

In this case, even if the composite mirror 11 has a thickness of t, when it receives electromagnetic waves radiated in the -y direction, it can collect them between focus P and focus Pt, regardless of the x coordinate.

1... inspection device, 11... composite mirror, 12... optical system, 13... detector, 14... parabolic mirror, 9... inspection system.

Claims (5)

A plurality of concave mirrors with different focal lengths are arranged so that their optical axes and foci overlap , and the equation is expressed using constants p and c1 and an independent variable x indicating the distance from the optical axis.
The inspection device inspects a person's belongings based on electromagnetic waves collected by a composite mirror having a curved surface rotated around the optical axis, the functional curve being : The inspection device according to claim 1 , wherein the composite mirror is disposed so as not to block the path of movement of the person. The inspection apparatus according to claim 1 or 2 , wherein the composite mirror has no gap when viewed from the focal point. 4. The inspection device according to claim 1, wherein the electromagnetic waves collected by the composite mirror are guided to a detector by an optical system disposed at the focal point. The inspection apparatus according to claim 4 , wherein the optical system is a polygon mirror.

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