KR20230121497A - Foreign matter detection device using terahertz wave - Google Patents

Abstract

A foreign material detection device using terahertz waves is disclosed.
The disclosed foreign matter detection device includes a source that outputs terahertz waves, a collimator that makes the terahertz waves parallel, a rotation reflector that reflects the terahertz waves that have passed through the collimator, and a terahertz wave reflected by the rotation reflector. and an f-theta lens that focuses on the subject.

Description

Foreign matter detection device using terahertz wave

An exemplary embodiment relates to a foreign material detection device using terahertz waves.

Terahertz wave (Terahertz wave) As an electromagnetic wave located in the region between infrared and microwave, it generally represents an electromagnetic wave having a frequency between 0.1 THz and 10 THz. Terahertz waves are sensitive to the structure and environment of the material molecules. In particular, since terahertz waves have lower energy than x-rays, an examination can be performed without causing deformation of the subject. Due to various characteristics of terahertz waves, such as straightness, permeability to materials, safety to living organisms, and possibility of qualitative confirmation, interest in terahertz waves continues to grow. As a result, various terahertz-selling airport or security facility inspection devices, food and pharmaceutical company quality inspection devices, semiconductor inspection devices, dental inspection devices, gas detection devices, explosives inspection devices, Lab-on-a-chip detectors, etc. applied in the field.

An exemplary embodiment provides a foreign material detection device capable of precisely detecting a foreign material using terahertz waves.

An exemplary embodiment provides a foreign material detection device capable of detecting a foreign material at high speed using terahertz waves.

An apparatus for detecting foreign matter using terahertz according to an exemplary embodiment includes a source outputting terahertz waves; a collimator that makes the terahertz waves parallel; a rotation reflector for reflecting the terahertz wave passing through the collimator; and an f-theta lens for concentrating the terahertz waves reflected by the rotation reflector onto an object under test, wherein the source is configured to output terahertz waves having a half divergence angle in the range of 3-20 degrees.

The foreign matter detection device using the terahertz wave satisfies the following equation.

<expression>

Here, f ₁ is the focal length of the collimator, and f ₂ is the focal length of the f-theta lens.

The f-theta lens may include a meniscus lens, and the meniscus lens may be configured to satisfy the following equation.

<expression>

Here, R ₁ is the radius of curvature of the incident surface of the meniscus lens, and R ₂ represents the radius of curvature of the exit surface of the meniscus lens.

The f-theta lens may include a meniscus lens and satisfy the following equation.

<expression>

Here, D ₁ is the diameter of the collimator, and D ₂ represents the diameter of the meniscus lens.

The f-theta lens may include a biconvex lens for receiving the terahertz wave reflected by the rotation reflector and a meniscus lens for receiving the terahertz wave passing through the biconvex lens.

The meniscus lens may have a meniscus shape convex toward the rotational reflector.

The f-theta lens may include a material having transmittance of 70% or more for waves in a frequency range of 0.1 to 10 terahertz.

The f-theta lens may include TPX or Teflon.

An apparatus for detecting foreign matter using terahertz waves according to an exemplary embodiment may increase detection accuracy by increasing a focusing speed of terahertz waves. In addition, high-speed inspection is possible by scanning terahertz waves using a rotation reflector.

1 illustrates a foreign material detection device using terahertz waves according to an exemplary embodiment.
FIG. 2 is a diagram for explaining a half divergence angle of a terahertz wave output from a source of a foreign matter detection device using terahertz waves according to an exemplary embodiment.
3 illustrates a foreign material detection device using terahertz waves according to another exemplary embodiment.
4 is a block diagram of a foreign material detection device using terahertz waves according to an exemplary embodiment.
FIG. 5 illustrates a focused intensity distribution of terahertz waves in a scanning direction according to rotation of a rotation reflector on a surface of an object under examination by the foreign matter detection apparatus according to the embodiment shown in FIG. 1 .
FIG. 6 illustrates a focused intensity distribution of terahertz waves in a scanning direction according to rotation of a rotation reflector on a surface of an object under examination by the foreign matter detection apparatus according to the embodiment shown in FIG. 3 .

Hereinafter, a foreign material detection apparatus using terahertz waves according to various embodiments will be described in detail with reference to the accompanying drawings. In the following drawings, the same reference numerals denote the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of description. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. Terms are only used to distinguish one component from another.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In addition, when a certain component is said to "include", this means that it may further include other components without excluding other components unless otherwise stated. In addition, the size or thickness of each component in the drawings may be exaggerated for clarity of explanation. Also, when it is described that a predetermined material layer is present on a substrate or another layer, the material layer may exist in direct contact with the substrate or other layer, and another third layer may exist in between. In addition, since the materials constituting each layer in the following examples are exemplary, other materials may be used.

In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software. .

Specific implementations described in this embodiment are examples, and do not limit the technical scope in any way. For brevity of the specification, description of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection of lines or connecting members between the components shown in the drawings are examples of functional connections and / or physical or circuit connections, which can be replaced in actual devices or additional various functional connections, physical connection, or circuit connections.

The use of the term “above” and similar denoting terms may correspond to both singular and plural.

Steps comprising a method may be performed in any suitable order, unless expressly stated that they must be performed in the order described. In addition, the use of all exemplary terms (for example, etc.) is simply for explaining technical ideas in detail, and the scope of rights is not limited due to these terms unless limited by claims.

1 illustrates a foreign material detection device using terahertz waves according to an exemplary embodiment.

A foreign matter detection device 1 using terahertz waves includes a source 10 that outputs terahertz waves (TW) and a collimator 20 that makes the terahertz waves (TW) output from the source 10 parallel to each other. , The rotational reflector 30 that reflects the terahertz wave (TW) that has passed through the collimator 20, and the terahertz wave (TW) reflected from the rotational reflector 30 is focused on the subject 50 F -Includes a theta lens (40).

The terahertz wave (TW) may have a frequency of 0.1 THz to 10 THz. Terahertz waves (TW) have characteristics that are easily absorbed in a medium such as water or oxygen, and have excellent refraction and diffraction characteristics for the medium. Terahertz waves (TW) are capable of penetrating plastics or fibers, and have the transmittance of radio waves and the straightness of light waves at the same time. Due to these characteristics, the subject 50 can be accurately identified, and high resolution can be obtained. Since the terahertz wave shows different transmission characteristics according to the conductivity characteristics of the object 50 under test, it can be applied to various fields. For example, terahertz waves (TW) can be applied to non-destructive testing such as security screening or food or material inspection.

FIG. 2 shows a half divergence angle θ of a terahertz wave TW output from the source 10 . The half divergence angle θ represents an angle between the central axis OA and the outermost line of the terahertz wave TW output from the source 10 when the terahertz wave diverges. The source 10 may be configured to output a terahertz wave (TW) having a half divergence angle (θ) in the range of 3-20 degrees. When the terahertz wave (TW) has such a half divergence angle range, the terahertz wave (TW) can be safely and accurately focused on the subject 50 .

The collimator 20 is disposed between the source 10 and the rotational reflector 30 and converts the terahertz wave (TW) output from the source 10 into a parallel beam so that the terahertz waves reflected from the rotational reflector 30 The scanning linear velocity of the wave TW can be made constant. The collimator 20 may be a biconvex lens. However, the shape of the collimator 20 is not limited thereto.

The rotation reflector 30 may be a rotatable polygonal mirror, for example, a hexagonal mirror. The rotation reflector 30 may be rotated by a motor M. As the rotation reflector 30 rotates, the terahertz wave (TW) may be scanned to the object 50 in a first direction (X direction). As the terahertz wave (TW) is scanned along the first direction (X direction) from the object 50 under test, a wide range of the object 50 under test may be inspected. Meanwhile, when the test is to be performed on the object 50 in the second direction (direction Y), the object 50 is moved in the second direction (direction Y) and then the terahertz wave (TW) is transmitted to the rotational reflector. While scanning by (30), the subject 50 of another line can be inspected. The first direction (X direction) and the second direction (Y direction) may form a right angle.

The f-theta lens 40 may focus the terahertz wave (TW) into a line shape. The f-theta lens 40 may include one or two lenses, and may include at least one meniscus lens. When the f-theta lens 40 includes at least one meniscus lens, the terahertz waves refracted by the f-theta lens 40 may be accurately focused on a specific area. 1 shows an example in which the f-theta lens 40 is composed of one meniscus lens 40a. The meniscus lens 40a may have a concave meniscus shape toward the rotational reflector 30 .

Meanwhile, in FIG. 3 , the f-theta lens 40 includes a biconvex lens 41 and a meniscus lens 42 . The f-theta lens 40 includes a biconvex lens 41 that receives the terahertz waves reflected by the rotation reflector 30 and a meniscus lens that receives the terahertz waves that have passed through the biconvex lens 41 (42) may be included. Elements using the same reference numerals as those in FIG. 1 in FIG. 3 are substantially the same as those described above, and thus detailed descriptions thereof are omitted. The meniscus lens 42 may have a convex meniscus shape toward the rotational reflector 30 .

An apparatus for detecting foreign matter using terahertz waves according to an exemplary embodiment may satisfy the following equation.

<Equation 1>

Here, f ₁ is the focal length of the collimator 20 and f ₂ is the focal length of the f-theta lens 40 .

Equation 1 represents the focal length ratio of the collimator 20 and the f-theta lens 40, and is related to the foreign material detection resolution and the distance between the object 50 and the foreign material detection device. The minimum detectable size of the subject 50 may be determined by the convergence size of the terahertz wave (TW) in the subject 50 . In other words, the inspection resolution of the object 50 under examination may vary according to the degree of convergence of the terahertz wave (TW). The focusing size of the terahertz wave (TW) can be adjusted by the focal length ratio of the collimator 20 and the f-theta lens 40 and the size of the oscillation or divergence of the source 10 of the terahertz wave (TW). . In FIG. 3 , the focal length of the f-theta lens 40 represents the combined focal length of the biconvex lens 41 and the meniscus lens 42 .

The lower limit value of Equation (1) means that the focal length of the f-theta lens 40 becomes very long, and if (f1/f2) has a value less than or equal to the lower limit value of Equation (1), the subject is inspected for foreign matter It means too far away from the device. In addition, if (f1/f2) exceeds the upper limit of Equation (1), the size of the subject that can be detected becomes too large because the size of the focused terahertz wave on the surface of the subject becomes too large to detect small-sized foreign matter. It becomes difficult to do. Accordingly, when Equation (1) is satisfied, the inspected object can be positioned at an appropriate position from the foreign material inspection device, and the foreign material detection resolution of the inspected object can be increased.

The f-theta lens 40 may include the meniscus lenses 40a and 42, and the meniscus lenses 40a and 42 may satisfy the following equation.

<Equation 2>

Here, R ₁ is the radius of curvature of the entrance surfaces S4 and S6 of the meniscus lenses 40a and 42, and R ₂ is the radii of curvature of the exit surfaces S5 and S7 of the meniscus lenses 40a and 42, respectively. ) represents the radius of curvature. The incident planes S4 and S6 represent planes on which the terahertz wave TW is incident, and the exit planes S5 and S7 represent planes from which the terahertz wave TW is emitted.

Equation (2) shows the condition for focusing the terahertz wave (TW) in a specific area. This is a condition for concentrating terahertz waves in a specific area. If (R2/R1) exceeds the upper limit value, optical aberration may increase and the focusing speed may decrease.

Next, an apparatus for detecting foreign matter using terahertz waves according to an exemplary embodiment may satisfy the following equation.

<Equation 3>

Here, D ₁ is the diameter of the collimator 20, and D ₂ represents the diameter of the meniscus lenses 40a and 42.

Equation (3) represents the diameter ratio of the meniscus lenses 40a and 42 to the collimator 20, and limits the size range of the collimator 20 and the meniscus lenses 40a and 41. A source that outputs terahertz waves is generally considerably smaller than the size of the surface of the object 50 under test. Accordingly, the size of the collimator 20 disposed close to the source 10 is smaller than the size of the f-theta lens 40 relatively close to the subject 50 . When (D1/D2) satisfies Expression (3), the foreign matter detection device by optimizing the sizes of the collimator 20 and the meniscus lenses 40a and 41 with respect to the source 10 and the object 50 The total size of can be minimized. When (D1/D2) exceeds the upper limit value of Equation (3), the size of the collimator 20 becomes too large and the size of the rotation reflector 30 and the f-theta lens 40 becomes too large, and the lower limit value If it is less than the focal length of the collimator 20, the focal length of the collimator 20 may be too short, and the size of focusing of the terahertz wave on the subject surface may be too large.

4 is a block diagram of a foreign material detection device using terahertz waves according to an exemplary embodiment. As described above, the foreign matter detection device includes a source 10 emitting terahertz waves, a collimator 20, a rotational reflector 30, and an f-theta lens 40 that focuses terahertz waves onto the subject 50. ) may be included. In addition, a receiver 60 that receives terahertz waves reflected from or transmitted through the object 50 under test and a foreign substance detector 65 that analyzes the signal received by the receiver 60 and detects foreign substances may be further provided.

An apparatus for detecting a foreign substance according to an exemplary embodiment connects terahertz waves emitted from a source 10 to an object 50 under test and measures a signal of a terahertz wave transmitted through the object 50 under test or ), the signal of the reflected wave can be measured.

The receiver 60 may output the intensity of the terahertz wave, and the foreign matter detector 65 may detect the foreign substance by analyzing the intensity of the terahertz wave. When a foreign substance is detected, the occurrence of the foreign substance may be notified to the user through the alarm unit 70 . The alarm unit 70 may emit a sound or be displayed on a display.

In addition, as the rotation reflector 30 rotates, the terahertz waves may be scanned in one direction of the object 50 under test. Therefore, the foreign matter inspection may be performed up to a certain range in one direction of the subject 50 . Meanwhile, a moving unit 55 for moving the object 50 under examination may be provided so that the object 50 under examination may be inspected in a different direction. The moving unit 55 may include, for example, a conveyor belt. Using this, the inspected object 50 can be inspected at high speed over a wide range.

FIG. 5 shows a focused intensity distribution of terahertz waves in a scanning direction according to the rotation of the rotation reflector 30 on the surface of an object under examination by the foreign matter detection apparatus according to the embodiment shown in FIG. 1, and FIG. FIG. 3 illustrates a focused intensity distribution of terahertz waves in a scanning direction according to the rotation of the rotation reflector 30 on the surface of a subject by the foreign matter detection apparatus according to the embodiment shown in FIG. 3 . In the distribution of the focused intensity of the terahertz wave, red color means high intensity, and blue means low intensity. Overall, the terahertz waves are well focused. In FIG. 1, the diameter of the collimator 20 is approximately 9.0 mm, and the diameter of the meniscus lens 40a is approximately 175.3 mm. 3, the diameter of the collimator 20 is approximately 37.5 mm, and the diameter of the meniscus lens 42 is approximately 165.2 mm.

A terahertz wave is a type of electromagnetic wave and has a wavelength between radio waves and visible light, and may have a wavelength ranging from approximately 0.3 mm to 3 mm. These terahertz waves are harmless to the human body, and even if they are of the same color, they react with materials of different subjects, so that foreign substances and abnormal tissues in the living body can be inspected. In order to perform high-speed examination on different subjects, terahertz waves must be scanned at high speed. To this end, the terahertz waves are made into a collimated beam by the collimator 20 and reflected by the rotation reflector 30 to scan the terahertz waves. When the rotation reflector 30 is rotated at high speed, the location of the focused terahertz waves may be changed. At this time, depending on the end and state of the object 50 under test, a change in the terahertz wave may be detected and a foreign substance may be detected using the change.

The f-theta lens 40 may include a material having transmittance of 70% or more for waves in a frequency range of 0.1 to 10 terahertz. For example, the f-theta lens 40 may include methyl-pentene copolymer (TPX) or Teflon. When the transmittance of the terahertz wave to the subject is high, the intensity of focusing of the terahertz wave (TW) emitted from the source 10 on the surface of the subject can be increased. In addition, the collimator 10 and the f-theta lens 40 may have a refractive index of 1.4 to 1.5 for terahertz waves.

The following shows design data for each component of the foreign matter detection device using terahertz waves shown in FIG. 1 . In the table, the unit of curvature radius, thickness and spacing, and focal length is mm, and inf represents infinity. As for the surface number, the incident surface of the collimator 20 was designated as S1, and the incident surface and exit surface of each component were named S2, S3, and S4?? in order.

side number radius of curvature thickness and spacing refractive index focus
distance Component inf. 18.45 Terahertz wave source S1 29.786 4 1.463 20.4 collimator S2 -13.243 20 S3 inf. 110 rotation reflector S4 -906.59 19 1.463 750.781 f-theta lens S5 -252.935 755.415 inf. subject

The following shows design data for each component of the foreign matter detection device using terahertz waves shown in FIG. 3 .

side number curvature
radius thickness and spacing refractive index focus
distance Component inf. 245 1.49 Terahertz wave source S1 156.142 27.86 236.375 collimator S2 -422.179 35 S3 inf. 24 rotation reflector S4 185.878 22 1.49 421.293 f-theta lens S5 -1000 91.9 S6 295.144 9.4 1.49 S7 171.411 235.134 inf. subject

As described above, the foreign matter detection apparatus using terahertz waves according to an exemplary embodiment increases detection resolution by focusing terahertz waves and scans terahertz waves using a rotational reflector, thereby enabling high-speed inspection. When terahertz waves are irradiated with air bubbles, cracks, metal materials, foreign substances, etc., they show reflection or transmission characteristics different from those of general transmission objects. there is.

The above embodiments are merely exemplary, and various modifications and equivalent other embodiments may be made therefrom by those skilled in the art. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the invention described in the following claims.

TW: terahertz wave, 10: source
20: collimator, 30: rotation reflector
40: f-theta lens, 41: biconvex lens
40a, 42: meniscus lens
50: subject

Claims (8)

a source outputting terahertz waves;
a collimator that makes the terahertz waves parallel;
a rotation reflector for reflecting the terahertz wave passing through the collimator; and
An F-theta lens for concentrating the terahertz waves reflected by the rotation reflector onto an object under test;
A foreign material detection device using terahertz waves, wherein the source is configured to output terahertz waves having a half divergence angle in the range of 3-20 degrees. According to claim 1,
A foreign material detection device using terahertz waves that satisfies the following equation.
<expression>

Here, f ₁ is the focal length of the collimator, and f ₂ is the focal length of the f-theta lens. According to claim 1,
The foreign matter detection device using terahertz waves, wherein the f-theta lens includes a meniscus lens, and the meniscus lens is configured to satisfy the following equation.
<expression>

Here, R ₁ is the radius of curvature of the incident surface of the meniscus lens, and R ₂ represents the radius of curvature of the exit surface of the meniscus lens. According to claim 1,
wherein the f-theta lens comprises a meniscus lens;
A foreign material detection device using terahertz waves that satisfies the following equation.
<expression>

Here, D ₁ is the diameter of the collimator, and D ₂ represents the diameter of the meniscus lens. According to claim 1,
The f-theta lens includes a biconvex lens for receiving the terahertz wave reflected by the rotation reflector, and a meniscus lens for receiving the terahertz wave passing through the biconvex lens. Foreign matter detection device. According to claim 5,
The meniscus lens has a convex meniscus shape toward the rotational reflector, the foreign matter detection device using terahertz waves. According to claim 1,
The foreign matter detection device using terahertz waves, wherein the f-theta lens includes a material having a transmittance of 70% or more for waves in the 0.1 to 10 terahertz frequency range. According to claim 1,
A foreign material detection device using terahertz waves, wherein the f-theta lens includes TPX or Teflon.

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