JP7075632B2 - Paper leaf inspection device using terahertz wave irradiation device - Google Patents

Description

The present invention relates to an inspection device for paper sheets using a terahertz wave irradiation device for irradiating a terahertz wave.

In recent years, various detection devices using terahertz waves have been proposed. For example, Patent Document 1 below proposes an inspection device for inspecting foreign matter adhering to inspected items such as banknotes in a non-contact manner at high speed and with high efficiency.

In this inspection device, the terahertz wave from the oscillator is mechanically changed in angle by a mirror such as a galvano mirror to irradiate the entire object to be inspected such as banknotes, or the irradiated part is divided into a plurality of regions. By arranging an oscillator in each area and irradiating it, the entire object to be inspected such as banknotes was irradiated.

According to such an inspection device, a terahertz wave can be applied to the entire inspected object such as a banknote for inspection, and a foreign substance such as a tape attached to the inspected item such as a banknote can be inspected at high speed without contact. Moreover, it was possible to detect with high efficiency.

Japanese Unexamined Patent Publication No. 2016-80452

However, in the terahertz wave irradiation device provided in the conventional inspection device, in the case of a device that irradiates the entire object to be inspected such as banknotes by mechanically changing the angle of the mirror, the change in the angle of the mirror causes the banknotes and the like. In order to irradiate the entire length of the inspected object, it was necessary to provide a long distance from the mirror to the inspected object such as banknotes, and the device tended to be large. In addition, it was not easy to keep the mirror's precise high-speed operation stable due to vibration.

Furthermore, when the irradiated area is divided into a plurality of areas and an oscillator is placed in each area for irradiation, although it is resistant to vibration, it is controlled by providing oscillators, lenses, etc. for the number of areas where the irradiated area is divided. This had to be done, and the device configuration tended to be complicated.

Therefore, an object of the present invention is to provide an inspection device for paper sheets using a terahertz wave irradiation device capable of stably irradiating a terahertz wave for a long period of time with a simple structure and easy miniaturization.

The inspection device of the present invention that achieves the above object is an inspection device for paper leaves using a terahertz wave irradiation device, and is a transport device for transporting the paper leaves to be inspected and a paper conveyed by the transport device. A terahertz wave irradiator that irradiates a terahertz wave from one side of a leaf and a detection device that detects a transmitted wave or a reflected wave from a paper leaf are provided, and the terahertz wave irradiator includes an oscillator and an oscillator. A rod-shaped waveguide including a waveguide that internally waveguides a terahertz wave from the oscillator and irradiates the terahertz wave over the entire length in the longitudinal direction or the lateral direction of the paper leaves at the irradiation position of the carrier. It is made of a transmissive material that does not transmit visible light and can transmit terahertz waves, and has a rod-shaped waveguide extending linearly in one axis direction, and the rod-shaped waveguide is provided at one end. The incident part of the terahertz wave, the emitting part for emitting the terahertz wave provided on one side surface, and the other side surface facing the one side surface where the emitting part is provided are provided at a position and a length corresponding to the emitting part. It has a prism part with a concavo-convex shape, and a lens part is provided on the oscillator side of the incident part. A resonator is formed in the space between the oscillator and the lens part of the incident part, and a waveguide is formed from the incident part. The terahertz wave that is waveguideed toward the other end side of the inside is refracted or reflected by the prism portion and emitted from the exit portion , and the detection device processes the detection element and the detection result by the detection element to generate foreign matter. It is equipped with an information processing unit that determines the presence / absence and position, and the two-dimensional intensity distribution of transmitted or reflected waves when the information processing unit detects paper leaves with no foreign matter attached to them and foreign matter adheres during inspection. By comparing with the two-dimensional intensity distribution of the transmitted wave or the reflected wave when the paper leaf is detected, it is detected whether or not foreign matter is attached to the front surface or the back surface of the paper leaf .

In the paper leaf inspection apparatus of the present invention, the permeation material may be any of high-resistance silicon, gallium arsenide, and indium phosphide. The prism portion has a plurality of concavo-convex portions formed in the other side surface, and the larger the distance from one end of the waveguide, the larger the size of the concavo-convex portion may be provided. Further, the prism portion may have a plurality of uneven portions formed in the other side surface, and may be provided so that the density of the uneven portions increases as the distance from one end of the waveguide increases. .. Further, the prism portion has a plurality of concavo-convex portions formed in the other side surface, and the farther the distance from one end of the waveguide is, the larger the inclination angle of the upstream surface portion in each concavo-convex portion is. It may be provided in.

In the paper leaf inspection apparatus of the present invention, the prism portion may have a refractive index changing portion in which an impurity is contained in the transmissive material and the refractive index is changed. In that case, the prism portion may be provided with a refractive index changing portion so that the concentration of impurities increases as the distance from one end of the waveguide increases.

In the paper leaf inspection apparatus of the present invention, terahertz waves can be incident from both ends of the waveguide, and the terahertz waves incident from each end are guided toward the other end side from one side surface. It may be possible to emit.
The irradiator is provided with a case for the irradiator that accommodates the waveguide, and the emitter of the waveguide is arranged in the case for the irradiator so as to emit terahertz waves to the paper sheets, and the oscillator is for the irradiator. It may be connected to the case.
A fiber plate may be interposed between the emitting part and the paper leaves and / or between the paper leaves and the detection element.

According to the present invention, a terahertz wave is waveguideed while traveling straight and internally reflected from one end side to the other end side inside the waveguide portion, and is refracted or reflected by the prism portion and emitted from the side surface. Therefore, by arranging the side surface of the waveguide close to the irradiated portion and oscillating the terahertz wave from one end side, the terahertz wave can be easily irradiated to the irradiated portion. By providing the waveguide with a prism portion corresponding to the total length of the irradiated portion, the terahertz wave can be easily applied to the entire length of the irradiated portion even in the irradiated portion having a long total length.

Even if the total length of the irradiated part is long, the side surface of the waveguide may be placed close to the irradiated part, the waveguide does not need to be separated from the irradiated part, and the waveguide is terrahertz from the end side. It suffices to inject the wave into the waveguide, and it is not necessary to use a large number of oscillators. Therefore, it is easy to significantly reduce the size of the irradiation device.
Furthermore, in order to irradiate the entire length of the irradiated area, it is not necessary to drive the waveguide, no drive mechanism or anti-vibration mechanism is required, and the waveguide is made inside the waveguide to refract or reflect it. The number of components that make up the waveguide can be reduced, and the configuration can be simplified. Therefore, it is not easily affected by vibration and the usage environment, and can stably irradiate terahertz waves for a long period of time.

Therefore, according to the present invention, it is possible to provide a terahertz wave irradiation device capable of stably irradiating a terahertz wave for a long period of time with an easy miniaturization and a simple configuration.

It is a figure explaining the inspection apparatus using the terahertz wave irradiation apparatus which concerns on 1st Embodiment of this invention, (a) is a front view, (b) is a right side view. It is a perspective view which shows the waveguide in the terahertz wave irradiation apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the waveguide in the terahertz wave irradiation apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the 1st modification of the waveguide in the terahertz wave irradiation apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the 2nd modification of the waveguide in the terahertz wave irradiation apparatus which concerns on 1st Embodiment of this invention. It is a top view which shows the 3rd modification of the waveguide in the terahertz wave irradiation apparatus which concerns on 1st Embodiment of this invention. It is sectional drawing of the waveguide in the terahertz wave irradiation apparatus which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the example which raised the incident efficiency of the terahertz wave to the waveguide in the irradiation apparatus of the terahertz wave in the 1st embodiment or the 2nd embodiment. It is sectional drawing which shows the structure of the terahertz wave irradiation apparatus which concerns on 3rd Embodiment. It is sectional drawing which shows the structure of the terahertz wave irradiation apparatus which concerns on 4th Embodiment, (a) is the front view, (b) is the right side view, (c) is the perspective view which shows the structure of a fiber plate, (d). ) Is a schematic perspective view showing the shape of the optical fiber constituting a part of the fiber plate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[First Embodiment]
In this embodiment, an example of a terahertz wave irradiation device incorporated in the inspection device will be described. As an example of the use of this inspection device, it is applied to a device for inspecting whether or not foreign matter such as transparent tape is attached to the front surface or the back surface of paper sheets as shown below.
1A and 1B are views for explaining an inspection device using the terahertz wave irradiation device according to the first embodiment of the present invention, where FIG. 1A is a front view and FIG. 1B is a right side view.
As shown in FIGS. 1 (a) and 1 (b), the inspection device 10 has one surface of a transport device 12 for transporting the paper leaves 11 to be inspected and a paper leaf 11 transported by the transport device 12. It includes an irradiation device 20 that irradiates terahertz waves from the side, and a detection device 30 that detects transmitted waves on the other surface side of the paper sheets 11.

The paper leaves 11 to be irradiated with the terahertz wave are rectangular banknotes and the like, and the entire surface of one surface is the irradiated portion.
The transport device 12 transports the paper leaves 11 in the direction along the surface, and the transport guides 13 are placed on the upper and lower portions of the paper leaves 11 so as to pass the terahertz wave irradiation position 12a in the lateral direction or the longitudinal direction. It has a structure in which 13 is arranged. Resin or glass can be used as the members of the transport guides 13 and 13.
The irradiation device 20 includes an oscillator 21 and a waveguide 22 that internally waveguides a terahertz wave from the oscillator 21 and irradiates the paper sheets 11 at the irradiation position 12a of the transfer device 12.

The oscillator 21 has an oscillating element such as a gunn diode, an IMPATT diode, various diodes such as a tannet diode, and a transistor formed from a compound semiconductor such as Si, GaAs or InP, and has 30 GHz (GHz is 10). It is capable of emitting terahertz waves in the frequency band of ⁹ Hz) to 12 THz. The oscillator 21 is preferably installed on a metal plate having excellent thermal conductivity such as a copper plate or an aluminum plate. By further thermally connecting the metal plate to a metal member such as a housing, the heat dissipation area can be expanded and the heat dissipation effect can be improved.

FIG. 2 is a perspective view showing a waveguide 22 in the terahertz wave irradiation device 20 according to the first embodiment of the present invention, and FIG. 3 is a cross-sectional view showing the waveguide 22 shown in FIG. As shown in FIG. 3, the waveguide 22 is formed in a substantially rod shape from a transmissive material capable of transmitting terahertz waves. In this embodiment, it has a prismatic shape or a semi-cylindrical shape and extends linearly in the uniaxial direction. Although not particularly limited, the kamaboko shape has a plane extending in a uniaxial direction and a convex curved surface protruding outward between both edges of the plane. The transmitting material may be a material that does not transmit visible light, but a material having as high a transmittance of terahertz waves as possible is preferable, and for example, high resistance silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), etc. Can be exemplified.

The waveguide 22 of the present embodiment includes an incident portion 23 provided at one end, a prism portion 24 that refracts or reflects a terahertz wave that is incident and guided from the incident portion 23 to the inside, and a prism portion. It has a side emitting portion 25 for emitting a terahertz wave from 24. The incident portion 23 is provided at one end of the waveguide 22, and the terahertz wave from the oscillators 21 arranged opposite to each other is incident on the inside of the waveguide 22 in the axial direction. The inside of the waveguide 22 is a waveguide 26 for the terahertz wave, and the terahertz wave is guided straight from one end side having the incident portion 23 toward the other end side while being internally reflected.

The emitting portion 25 provided on one side surface is a smooth flat surface in the case of the prism-shaped waveguide 22, and is an outward convex curved surface in the case of the Kamaboko-shaped waveguide 22. A terahertz wave is emitted according to the shape and direction of the emitting portion 25. The emission unit 25 is continuously provided in the light guide direction of the waveguide 26, and the terahertz wave is emitted from the emission unit 25 in a line shape. In the present embodiment, the emitting portion 25 of the waveguide 22 is fixedly arranged so as to face the irradiation position 12a of the conveying device 12.

The prism portion 24 is formed in a concavo-convex shape at a position and length corresponding to the emitting portion 25 on the opposite side surface different from the one side surface on which the emitting portion 25 is provided. In the present embodiment, by denting in a streak shape from the side surface opposite to the exit portion 25, a plurality of streak-shaped recesses 27 having a polygonal shape such as a substantially triangular cross section are formed in a saw blade shape to form a prism. The unit 24 is configured. Instead of denting into a polygonal shape such as a substantially triangular cross section, a refraction or reflection member having the same shape may be fitted, and the streak recess 27 is hereinafter referred to as a streak uneven portion 27. A plurality of streaky uneven portions 27 are formed in the waveguide 22.

In the present embodiment, each streak-like uneven portion 27 is formed so as to cross the entire width of the other side surface in a direction intersecting the waveguide direction and parallel to each other. Although not particularly limited, each streak-like uneven portion 27 may be formed orthogonal to the central axis of the waveguide 26 inside the waveguide 22.

In the prism portion 24, the larger the distance from the one end side where the incident portion 23 of the waveguide 22 is provided, the larger the size of the streak-like uneven portion 27 (in the case of a concave portion, the deeper the depth). There is. That is, the size d1 of the streak-like uneven portion 27 is smaller toward the one end side having the incident portion 23 (the depth d1 is shallower in the case of the concave portion), and the size d2 of the streak-like uneven portion 27 is larger toward the other end side. (In the case of a recess, the depth d2 is deep).

As a result, the terahertz wave guided from the incident portion 23 is refracted or reflected by the uneven surfaces of the plurality of streaky uneven portions 27 of the prism portion 24, and is emitted from the emitting portion 25 in a line shape. Then, by devising the number and size of these plurality of streaky uneven portions 27, the arrangement interval, and the shape of the surface that refracts or reflects the terahertz wave to be waveguideed, the light is emitted in this line shape. The terahertz wave can be made as uniform as possible in the entire length, and the entire length in the longitudinal direction of the paper sheets 11 moving at the irradiation position 12a of the transport device 12 can be irradiated.

The detection device 30 for detecting the transmitted wave on the other surface side of the paper sheet 11 is waveguideed via, for example, a light-condensing optical component 31 including a frenell lens, a convex lens, a concave lens, and the like, and a light-condensing optical component 31. A large number of detection element groups 33 composed of shotkey barrier diodes 32a to 32n and the like arranged linearly so as to face the emission unit 25 of the body 22, and the detection results of the detection element group 33 are transferred information of the transfer device 12 and the like. It has an information processing unit 34 that determines the presence / absence and position of foreign matter by processing both. The Schottky barrier diodes 32a to 32n are mounted on the printed circuit board 35, for example.
The information processing unit 34 has a two-dimensional intensity distribution of the transmitted wave when the paper leaf 11 having no foreign matter adhered to the paper leaf 11 and a transmission when the paper leaf 11 having foreign matter adhered to the paper leaf 11 is detected. It is configured to detect whether or not foreign matter is attached by comparing it with the two-dimensional intensity distribution of the wave.

In this inspection device 10, when the paper leaves 11 are transported by the transport device 12, they move in the lateral direction or the longitudinal direction with the front surface or the back surface facing the irradiation device 20 side and pass through the irradiation position 12a. .. The irradiation position 12a is irradiated with a line-shaped terahertz wave from the irradiation device 20 so as to cross the paper sheets 11 in the longitudinal direction or the lateral direction. When the paper leaves 11 pass through the irradiation position 12a, the line-shaped terahertz waves crossing the longitudinal direction or the lateral direction move relative to each other in the lateral direction or the longitudinal direction in order to irradiate the entire surface of the paper leaves 11. .. At the irradiation position 12a, the terahertz wave transmitted through the paper leaves 11 is detected by the detection device 30, and the information processing unit 34 detects whether or not foreign matter is attached to the paper leaves 11.

According to the terahertz wave irradiation device 20 of the present embodiment as described above, the terahertz wave is waveguideed straight from one end side to the other end side and internally reflected inside the waveguide 22, and is refracted by the prism portion 24. Or it reflects and emits from the side surface. Therefore, the side surface of the waveguide 22 is arranged close to the paper leaf 11 and the terahertz wave is waveguideed from one end side, so that the terahertz wave can be easily applied to the paper leaf 11. By providing the waveguide 22 with a prism portion 24 corresponding to the total length in the longitudinal direction or the lateral direction of the paper leaf 11, the terahertz wave can be easily applied to the entire length even if the total length is long.

Even if the total length is long, irradiation can be performed by arranging the side surface of the waveguide 22 close to the paper leaves 11, and it is not necessary to arrange the waveguide 22 so as to be separated from the paper leaves 11. A terahertz wave may be incident on the waveguide 22 from the end side of the waveguide 22, and it is not necessary to use a large number of oscillators. Therefore, the irradiation device 20 can be significantly miniaturized.

Further, it is not necessary to drive the waveguide 22 in order to irradiate the entire length of the paper sheets 11, and no driving mechanism or anti-vibration mechanism is required. Moreover, since the waveguide is wave-guided inside the waveguide 22 to be refracted or reflected, the number of components constituting the waveguide 26 can be reduced, and the configuration can be simplified. Therefore, it is not easily affected by vibration and the usage environment, and can stably irradiate terahertz waves for a long period of time.

According to the terahertz wave irradiation device 20, an emission unit 25 for emitting a terahertz wave is provided on one side surface of the waveguide 22, and an uneven prism portion 24 is provided on the other side surface corresponding to the emission unit 25. Is provided. Therefore, a part of the terahertz wave that is internally reflected and guided by the inner side surface of the waveguide 22 can be emitted from the emitting unit 25 by refracting or reflecting it at the prism unit 24, and the rest can be emitted to the downstream side. Can be transparent. As a result, the terahertz wave can be emitted from a wide range in the waveguide direction by providing the prism portion 24 having a concave-convex shape in a wide range in the waveguide direction.

According to the terahertz wave irradiation device 20, a plurality of streaky uneven portions 27 in which a prism portion 24 is formed by being recessed from another side surface or a refraction or reflection member matching the recessed shape is fitted are formed. The longer the distance from the incident portion 23 on one end side of the waveguide 22, the larger the size or the deeper the streak-like uneven portion 27 is. Therefore, in the waveguide 26 inside the waveguide 22, the ratio of refraction or reflection can be reduced on the upstream side where the terahertz wave arrives without being attenuated so much, and the ratio of refraction or reflection can be increased on the downstream side where the terahertz wave is attenuated and reached. can. As a result, the difference in the intensity of the terahertz waves emitted between the upstream side and the downstream side of the emitting unit 25 can be reduced, and can be made equivalent as much as possible.

The above embodiment can be appropriately changed within the scope of the present invention. For example, in the above, an example in which the terahertz wave irradiation device 20 is used as an inspection device for paper sheets 11 has been described, but the present invention is not limited to anything, and can be used for other purposes, for example, irradiation in a three-dimensional shape. It may be a device that irradiates a site with a terahertz wave, or may be a device that irradiates an organism such as a human body with a terahertz wave.

In the above embodiment, as the inspection device 10 using the irradiation device 20, the terahertz wave transmitted through the paper leaves 11 is detected by the detection device 30, but the present invention is not limited thereto. By providing a detection unit on the same side as the irradiation device 20 for the paper leaves 11, it is also possible to configure the terahertz waves reflected on the front surface or the back surface of the paper leaves 11 to be detected. In that case, the inclination angle of the emitting portion 25 of the waveguide 22 with respect to the paper leaves 11 may be larger than the above, and one side surface of the waveguide 22 provided with the emitting portion 25 may be formed diagonally. May be good. This makes it easier to detect the reflected wave.

Further, the waveguide 22 can be deformed in various ways. For example, in the above, a plurality of polygonal streaky uneven portions 27 are provided, but the waveguide 22 may not be streaky and may be provided with fine irregularities at random. ..

[First modification]
FIG. 4 is a cross-sectional view showing a waveguide 22 in the terahertz wave irradiation device 20 of the first modification. The waveguide 22 of the first modification has a structure in which the structure of the prism portion 24 is different from that of the above embodiment. In the prism portion 24 of this modification, a plurality of streaky uneven portions 27 having a substantially triangular cross section are formed on the side surface side different from the exit portion 25. Then, as in the above embodiment, the size or depth of the streak-like uneven portion 27 becomes larger or deeper as the distance from one end side having the incident portion 23 increases, and the density of the streak-like uneven portion 27 increases. It is provided in. That is, the pitch p1 between the streak-like uneven portions 27 adjacent to each other is larger toward one end side having the incident portion 23, and the pitch p2 between the streak-like uneven portions 27 is smaller toward the other end side. Others are the same as those in the above embodiment.

Even in such a first modification, the same effect as that of the above embodiment can be obtained. In particular, in the first modification, the longer the distance from one end side of the waveguide 22, the higher the density of the streak-like uneven portion 27. Therefore, in the waveguide 26 inside the waveguide 22, the ratio of refraction or reflection can be reduced on the upstream side where the terahertz wave arrives without being attenuated so much, and the ratio of refraction or reflection can be increased on the downstream side where the terahertz wave is attenuated and reached. can. As a result, the difference in the intensity of the terahertz waves emitted between the upstream side and the downstream side of the emitting unit 25 can be reduced, and in a remarkable case, the same can be achieved.

In this first modification, the size or depth of the plurality of streaky uneven portions 27 is the same size or depth without increasing or deepening as the distance from one end side having the incident portion 23 increases. It may be formed so that the density of the streak-like uneven portion 27 increases as the distance from one end side of the waveguide 22 increases.

[Second modification]
FIG. 5 is a cross-sectional view showing a waveguide 22 in the terahertz wave irradiation device 20 of the second modification. The waveguide 22 of the second modification has a structure in which the structure of the prism portion 24 is different from that of the above embodiment.
In the prism portion 24 of this modification, a plurality of streaky uneven portions 27 having a substantially triangular cross section are formed on the side surface side different from the exit portion 25. Then, as in the above embodiment, the size or depth of the streak-like uneven portion 27 becomes larger or deeper as the distance from one end side having the incident portion 23 increases, and the streak-like uneven portion arranged on the incident portion 23 side. The inclination angle of one surface of the portion 27, in other words, the inclination angle of one surface arranged on the upstream side where the terahertz wave is guided is increased, that is, the one end side having the incident portion 23 is streaked. The inclination angle θ1 of one surface arranged on the upstream side of the uneven portion 27 is small, and the inclination angle θ2 of one surface arranged on the upstream side is larger toward the other end side. Others are the same as those in the above embodiment.

Even in such a second modification, the same effect as that of the above embodiment can be obtained. In particular, in the second modification, the farther the distance from one end side of the waveguide 22 having the incident portion 23 is, the larger the inclination angle of one surface on the upstream side of each streak-like uneven portion 27 is provided. Therefore, in the waveguide 26 inside the waveguide 22, the rate of refraction or reflection can be reduced on the upstream side where the terahertz wave arrives without being attenuated so much, and the rate of refraction or reflection can be reduced on the downstream side where the terahertz wave arrives after being attenuated. You can make it bigger. As a result, the difference in the intensity of the terahertz waves emitted between the upstream side and the downstream side of the emitting unit 25 can be reduced and can be made as equal as possible.

In this second modification, the depths of the plurality of streaky uneven portions 27 are formed at the same depth without being deepened as the distance from one end side having the incident portion 23 is far, and one end of the waveguide 22 is formed. The farther the distance from the side is, the larger the inclination angle of the inner surface on the upstream side of each streak-like uneven portion 27 may be. Further, as in the first modification, the longer the distance from one end side of the waveguide 22 having the incident portion 23, the higher the density of the streak-like uneven portion 27, and the one end side of the waveguide 22. It may be provided so that the inclination angle of the inner surface on the upstream side of each streak-like uneven portion 27 becomes larger as the distance from the streak-like uneven portion 27 increases.

[Third modification example]
FIG. 6 is a cross-sectional view showing a waveguide 22 in the terahertz wave irradiation device 20 of the third modification. The waveguide 22 of the third modification is provided with terahertz wave incident portions 23 at both ends, and an oscillator 21 is arranged in each. In this waveguide 22, the terahertz wave incident from each end is guided toward the other end side, refracted or reflected by the prism portion 24 provided on the side surface, and can be emitted from the emission portion 25. .. In this case, a shielding portion 28 that shields the terahertz wave is provided at an intermediate position, and the terahertz wave from one incident portion 23 and the terahertz wave from the other incident portion 23 are irradiated to different regions. good. Others are the same as those of the above embodiment and the first and second modifications.

Also in the third modification, the same action and effect as those of the first embodiment can be obtained. In particular, in the third embodiment, since the terahertz wave is configured to be incident and emitted from both ends of the waveguide 22, a stronger terahertz wave is emitted from the side surface in the longitudinal direction of the paper sheet 11. It can irradiate the entire length.

[Second Embodiment]
FIG. 7 is a cross-sectional view of the waveguide 22 in the terahertz wave irradiation device 20 according to the second embodiment. The prism portion 24 of the waveguide 22 of the second embodiment has a refractive index changing portion 29 in which the refractive index is changed so as to be different from other portions by containing impurities in the transmission material as described above. ing. The impurities contained in the refractive index changing portion 29 can change the refractive index of the terahertz wave by diffusing into the above-mentioned transmissive material by doping or the like. For example, when the permeation material is high resistance silicon or the like, phosphorus (P), boron (B) or the like can be exemplified, and when the permeation material is gallium arsenic or indium phosphide, silicon (Si), zinc (Zn) or the like can be used. It can be exemplified.

Further, the prism portion 24 of the present embodiment is provided with a plurality of refractive index changing portions 29 having different refractive indexes due to different concentrations of impurities. In the prism portion 24, a plurality of refractive index changing portions 29 are provided adjacent to each other so that the longer the distance from the one end side of the waveguide 22 where the incident portion 23 is provided, the higher the concentration of impurities. .. Further, the depths of the refractive index changing portions 29 are provided so as to be different from each other, and the depth of the refractive index changing portions 29 is provided so as to be shallow in the region where the impurity concentration is low.

Such a refractive index changing portion 29 can be formed, for example, as follows. Impurities are diffused by masking predetermined portions of the left end portions 22a to 22e of the waveguide 22. When the transmissive material is high resistance silicon, SiO ₂ or the like can be used as a mask. The right end 22f of the waveguide 22 may not be masked for deep diffusion.
First, impurity diffusion is performed by diffusion (deposit or simply referred to as depot) or ion implantation only on the surface of the left end 22a to the right end 22f of the waveguide 22.
Next, the waveguide 22 can be diffused (also referred to as drive-in) for a predetermined time using a diffusion furnace to obtain a desired impurity density distribution.
Here, the diffusion furnace may have a temperature distribution that is non-uniform in the longitudinal direction of the waveguide 22, for example, an inclined temperature distribution. In this case, a sloped temperature distribution is formed from the left side end 22a to the right side end 22f of the waveguide 22, so if the right side end 22f of the waveguide 22 is set as the maximum temperature portion, this location. The diffusion depth is the highest. Since the temperature of the diffusion furnace decreases from the right end 22f of the waveguide 22 toward the left end 22a of the waveguide 22, the diffusion depth of the left end 22a of the waveguide 22 becomes the shallowest. As a result, the refractive index changing portion 29 can be formed on the waveguide 22.

Others can be configured in the same manner as in the first embodiment, and the terahertz wave irradiation device 20 can be configured in the same manner as in the first embodiment using the waveguide 22. Further, it is also possible to configure the incident portion 23 in the same manner as in the third modification.

Even with the terahertz wave irradiation device 20 of the second embodiment, the same effect as that of the first embodiment can be obtained. In particular, in the second embodiment, since the prism portion 24 has a refractive index changing portion 29 in which an impurity is contained in the transmissive material and the refractive index is changed, the prism portion 24 travels straight or internally reflects inside the waveguide 22. The terahertz wave to be waveguide can be refracted or reflected by the refractive index changing unit 29 and emitted from the emitting unit 25. Therefore, the terahertz wave can be easily applied to the entire length of the paper leaf 11 in the longitudinal direction by appropriately providing the refraction changing portion 29 containing impurities.

Further, in the prism portion 24, the refractive index changing portion 29 is provided so that the longer the distance from one end side of the waveguide 22 is, the higher the impurity concentration is. Therefore, in the waveguide 26 inside the waveguide 22 The rate of refraction or reflection can be reduced on the upstream side where the terahertz wave arrives without much attenuation, and the rate of refraction or reflection can be increased on the downstream side where the terahertz wave arrives after being attenuated. As a result, the difference in the intensity of the terahertz waves emitted between the upstream side and the downstream side of the emitting unit 25 can be reduced, and in a remarkable case, the same can be achieved.

It should be noted that the second embodiment can be appropriately changed as in the first embodiment within the scope of the present invention. For example, the refractive index changing portion 29 may be provided in each waveguide 22 of the first embodiment of FIGS. 2 to 6 as in the second embodiment to form a prism portion 24.

[Other variants]
FIG. 8 is a plan view showing an example in which the incident efficiency of the terahertz wave on the waveguide 22 according to the terahertz wave irradiation device 20 of the first embodiment or the second embodiment is increased. In this modification, the oscillator 21 in which the terahertz wave is oscillated is provided with a lens portion 21a having a convex surface protruding on the emission side, which is the waveguide 22 side. The waveguide 22 has an incident portion 23 of the waveguide 22 facing the oscillator 21 formed in a lens shape having a convex surface on the oscillator 21 side. Here, a spherical condensing lens is formed.

In this case, since the space between the oscillator 21 and the condenser lens of the incident portion 23 of the waveguide 22 becomes a resonator, the incident efficiency can be remarkably improved by adjusting the resonance points according to the wavelength. Therefore, in the irradiation device 20 of this modification, the distance between the oscillator 21 and the incident portion 23 is optimized according to the wavelength, and the incident efficiency is further improved.

In such a modification, the same effect can be obtained by combining with the waveguide 22 of the first embodiment having the uneven portion or the second embodiment having the refractive index changing portion. Can be done. In particular, in this modification, more terahertz waves from the oscillator 21 can be incident from the incident portion 23 of the waveguide 22, and the incident efficiency can be improved. That is, by forming the incident portion 23 in the shape of a lens, the influence of the interfacial reflection of the incident portion 23 can be reduced, whereby as much terahertz wave from the oscillator 21 can be incident on the waveguide 22. As a result, the irradiated portion can be more strongly irradiated with the terahertz wave. If the oscillator 21 can be arranged close to the waveguide 22 and the terahertz wave can be irradiated from the waveguide 22 with a desired intensity, it is possible not to provide the lens portion 21a on the oscillator 21.

[Third Embodiment]
Next, the third embodiment will be described.
FIG. 9 is a cross-sectional view showing the configuration of the terahertz wave irradiation device 50 according to the third embodiment. As shown in FIG. 9, the terahertz wave irradiation device 50 according to the third embodiment includes an oscillator 21, a waveguide 22, an irradiation device case 52 for holding the waveguide 22, and the like. There is. The oscillator 21 is fixed to the irradiation device case 52. When the irradiation device case 52 is made of metal, the radiator 21 can dissipate heat through the irradiation device case 52. The irradiation device 50 may further include a lens unit 21a in the oscillator 21 and an incident unit 23 in the waveguide 22.

According to the terahertz wave irradiation device 50, since the area of the irradiation device case 52 is larger than the area of the oscillator 21, the radiator 21 can easily dissipate heat. Further, the case 52 for the irradiation device may be installed on a metal plate having excellent thermal conductivity such as a copper plate or an aluminum plate to further dissipate heat.

Although the third embodiment is described in the modified example shown in FIG. 8 in which the oscillator 21 is provided with the lens portion 21a, the present invention is not limited to this, and the third embodiment is not limited to this, and the third embodiment is shown in FIGS. 1 to 7. It is a configuration applicable to the first embodiment or the second embodiment.

[Fourth Embodiment]
Next, the fourth embodiment will be described.
FIG. 10 is a diagram showing the configuration of the terahertz wave irradiation device 70 according to the fourth embodiment, in particular, FIG. 10 (c) shows the configuration of the fiber plate 71, and FIG. 10 (d) shows the fiber plate 71 of (c). The shape of the optical fever that constitutes a part of is shown. The terahertz wave irradiation device 70 according to the fourth embodiment has a fiber plate 71 interposed between the waveguide 22 and the irradiation position 12a of the transfer device 12. Here, the fiber plate 71 is a matrix of optical fibers 71a having a large number of minute diameters, as shown in FIGS. 10 (c) and 10 (d). The fiber plate 71 is a paper leaf in a state in which the terahertz wave emitted from the emitting portion 25 on the side surface of the substantially rod-shaped waveguide 22 is directed toward the detection device 30 arranged to face the waveguide 22. 11 is to be irradiated. That is, the terahertz wave emitted from the emitting portion 25 on the side surface of the substantially rod-shaped waveguide 22 is irradiated toward the detection device 30 in a state where there is no directivity, but by interposing the fiber plate 71, The detection device 30 can detect the terahertz wave transmitted through the paper leaves 11 with directivity, and can detect the two-dimensional intensity distribution of the transmitted wave of the paper leaves 11 with higher accuracy. In that sense, the fiber plate 71 may be interposed between the transport device 12 and the detection device 30, or may be provided on both sides. Others are the same as any of the above embodiments.

In the terahertz wave irradiation device 70, the fiber plate 71 is interposed between the waveguide 22 and the transfer device 12 for irradiating the paper leaves 11 with the terahertz wave and / or between the transfer device 12 and the detection device 30. Therefore, while maintaining the miniaturization of the irradiation device 70, the terahertz wave irradiating the paper leaves 11 and / or the terahertz wave transmitted through the paper leaves 11 can be made directional. It is possible to detect the two-dimensional intensity distribution of the transmitted wave of the paper leaf 11 with higher accuracy.

10 Inspection device 11 Paper leaf 12 Conveyor device 12a Irradiation position 13 Conveyance guide 20, 50, 70 Irradiation device 21 Oscillator 21a Lens unit 22 waveguide 23 Incident part 24 Prism part 25 Emission part 26 Waveguide path 27 Streak recess 28 Shielding unit 29 Refractive index change unit 30 Detection device 31 Optical component for condensing 32: Detection element 33 Detection element group 34 Information processing unit 35 Printed substrate 52 Irradiation device case 71 Fiber plate 71a Optical fiber

Claims (9)

It is an inspection device for paper leaves using a terahertz wave irradiation device.
A transport device that transports paper leaves to be inspected,
The terahertz wave irradiation device that irradiates the terahertz wave from one surface side of the paper sheets transported by the transfer device, and the terahertz wave irradiation device.
A detection device that detects transmitted waves or reflected waves from the paper sheets,
Equipped with
The terahertz wave irradiation device internally waveguides the terahertz wave from the oscillator and the terahertz wave from the oscillator to irradiate the entire length of the paper sheet in the longitudinal direction or the lateral direction at the irradiation position of the carrier device. With a wave body,
The waveguide is a rod-shaped waveguide that is made of a transmissive material that does not transmit visible light and is capable of transmitting terahertz waves and extends linearly in the uniaxial direction.
The rod-shaped waveguide is
The incident part of the terahertz wave provided at one end and
An emission unit that emits the terahertz wave provided on one side,
An uneven prism portion provided on the other side surface facing the one side surface on which the emission portion is provided and provided at a position and length corresponding to the emission portion.
Have,
A lens portion is provided on the oscillator side of the incident portion, and a resonator is formed in the space between the oscillator and the lens portion of the incident portion.
The terahertz wave waveguided from the incident portion toward the other end side inside the waveguide is refracted or reflected by the prism portion and emitted from the emitting portion .
The detection device includes a detection element and an information processing unit that processes the detection result of the detection element to determine the presence / absence and position of a foreign substance, and the information processing unit provides a sheet of paper on which no foreign substance adheres to the paper sheet. By comparing the two-dimensional intensity distribution of the transmitted or reflected wave when the paper is detected with the two-dimensional intensity distribution of the transmitted or reflected wave when the paper leaf to which foreign matter is attached is detected during the inspection, the paper leaf A paper leaf inspection device that detects whether or not foreign matter is attached to the front or back surface of the class . The paper leaf inspection apparatus according to claim 1, wherein the permeation material is any one of high-resistance silicon, gallium arsenide, and indium phosphide. The prism portion has a plurality of uneven portions formed in the other side surface, and the farther the distance from the one end portion of the waveguide is, the larger the size of the uneven portion is provided. , The paper leaf inspection apparatus according to claim 1. The prism portion has a plurality of concavo-convex portions formed in the other side surface, and is provided so that the density of the concavo-convex portion increases as the distance from one end of the waveguide increases. The paper leaf inspection apparatus according to claim 1. The prism portion has a plurality of uneven portions formed in the other side surface, and the farther the distance from the one end portion of the waveguide is, the more the inclination angle of the upstream surface portion in each of the concave-convex portions is. The paper leaf inspection device according to claim 1, which is provided so as to increase the size of the paper leaf. The prism portion has a refractive index changing portion in which an impurity is contained in the transmissive material to change the refractive index, and the concentration of the impurity increases as the distance from one end of the waveguide increases. The paper leaf inspection device according to claim 1, which is provided so as to be high. The claim that the terahertz wave can be incident from both ends of the waveguide, and the terahertz wave incident from both ends can be guided toward the other end and emitted from one side surface. The paper leaf inspection apparatus according to 1. The irradiation device includes an irradiation device case for accommodating the waveguide, and is arranged in the irradiation device case so that an emitting portion of the waveguide emits the terahertz wave to the paper sheets. The paper leaf inspection device according to claim 1, wherein the oscillator is connected to the irradiation device case. The paper leaf inspection apparatus according to claim 1, wherein a fiber plate is interposed between the emitting portion and the paper leaf and / or between the paper leaf and the detection element .

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