KR101738395B1 - High resolution detecting apparatus using terahertz bessel beam - Google Patents

Abstract

According to an embodiment of the present invention, a high resolution inspection apparatus using a terahertz bessel beam comprises: a terahertz wave generating unit for generating a terahertz wave; a bessel beam forming unit for forming a terahertz bessel beam on an object to be inspected using a terahertz wave from the terahertz wave generating unit; a first lens for changing an angle of the terahertz wave emitted while the terahertz bessel beam passes through the object to be inspected; a second lens for condensing the terahertz wave passed through the first lens to a detector; and a terahertz wave detecting unit for detecting a terahertz wave condensed by the second lens. The present invention intends to provide an inspection apparatus and a condensing module capable of increasing condensing efficiency of a terahertz bessel beam transmitted through an object to be inspected to increase resolution.

Description

TECHNICAL FIELD [0001] The present invention relates to a high-resolution inspection apparatus using a terahertz far-

The present invention relates to a technique for inspecting an object to be inspected by a non-destructive method using a terahertz wave, and to an inspection apparatus and a light collecting module having a high resolution below wavelengths beyond a diffraction limit.

In order to examine objects or substances in a non-destructive way, imaging methods are mainly used. Mainly, two methods of image detection using a continuous output light source and image detection using a spectroscopic method are mainstream. These methods have advantages and disadvantages, respectively, but image detection methods using continuous output light sources are widely used in fields requiring relatively high power such as transmission images.

Terahertz waves are widely used in the field of qualitatively identifying hidden objects or substances in a non-destructive way due to their excellent properties such as permeability to materials, possibility of qualitative confirmation, and safety to the living body.

In recent years, terahertz waves have been used in various fields such as airport and security facility search devices, food and pharmaceutical company quality inspection devices, semiconductor inspection devices, and engineering plastic inspection devices.

Terahertz waves are increasingly used in production sites, and continuous improvements have been made in terms of major performance indices such as detection resolution, detection speed, and detection area.

Previously, only a single lens was used to collect terahertz waves that were transmitted through an object to obtain terahertz paraffin images. In this case, if the apical angle of the axicon lens forming the vessel beam is made small so as to make the beam size of the terahertz wave focused on the object to be inspected less than the wavelength, the terahertz vessel beam passes through the object to be inspected, There arises a problem that the light is diverged and is not concentrated on the detection unit. Accordingly, the light-condensing property is remarkably reduced, and the signal-to-noise ratio (SNR) of the inspection apparatus is remarkably reduced, so that a normal image can not be obtained.

Korean Patent No. 10-1392311

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inspection apparatus and a light collecting module capable of increasing a light collecting efficiency of a terahertz beam beam transmitted through an object to be inspected and improving the resolution.

 Other objects and advantages of the present invention will become apparent from the following description, and it will be understood by those skilled in the art that the present invention is not limited thereto. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

A high resolution inspection apparatus using a vessel beam according to an embodiment of the present invention includes a terahertz wave generating unit for generating a terahertz wave and a terahertz wave generating unit for generating a terahertz wave using a terahertz wave generated from the terahertz wave generating unit, A first lens that changes an angle of a terahertz wave emitted from the terahertz Pervasell beam while passing through the object to be inspected, and a second lens that changes the angle of the terahertz wave transmitted through the terahertz Pervasell beam through the first lens, A second lens for converging a wave to a detector; And a terahertz wave detecting unit for detecting a terahertz wave condensed by the second lens.

The vessel beam forming unit may be a first axicon lens having a vertex angle in which the diameter of the terahertz wave plasma beam is smaller than the wavelength of the terahertz wave generated in the terahertz wave generating unit.

The first lens may be a second axicon lens arranged symmetrically with respect to the first axicon lens with reference to the object to be examined.

The second axicon lens may have an apex angle that is the same as that of the first axicon lens.

The high resolution inspection apparatus using the vessel beam may further include an angle changing unit for changing the angle of the terahertz wave incident from the terahertz generating unit to change the angle of the terahertz wave to be incident on the vessel beam forming unit.

Wherein the angle changing unit is a first convex lens for changing the angle of the terahertz wave incident from the terahertz generating unit to a small angle and the second lens is a second convex lens for deflecting the second convex lens arranged symmetrically to the first convex lens on the basis of the inspection object, Lt; / RTI >

The second lens may be a third axicon lens having the same shape as the second axicon lens and arranged symmetrically to the second axicon lens with respect to an axis perpendicular to the optical axis.

The first lens may be a third convex lens that changes the angle of the terahertz wave that is emitted while the terahertz Farber beam penetrates the object.

The second lens may be a fourth convex lens disposed symmetrically with respect to the third convex lens with respect to an axis perpendicular to the optical axis.

According to an embodiment of the present invention, there is provided a high-resolution terahertz wave condensing module including: a first lens that changes an angle of a terahertz wave emitted from a terahertz wavelength laser beam through an object; And a second lens for converging the terahertz wave passed through the first lens to a detector.

The first lens forms the terahertz spectacle beam on the basis of the object to be inspected, and the diameter of the terahertz wave incident on the detector is formed to be smaller than the wavelength of the terahertz wave generated in the terahertz wave generator And a second axicon lens disposed symmetrically to the first axicon having a vertex angle.

The second axicon lens may have an apex angle that is the same as that of the first axicon lens.

The second lens may be a second convex lens arranged symmetrically with respect to the first convex lens for changing the angle of the terahertz wave incident from the terahertz generating unit to a small value with reference to the object to be inspected.

The second lens has the same shape as the second axicon lens and may be disposed symmetrically with respect to the second axicon lens with respect to an axis perpendicular to the optical axis.

The first lens may be a third convex lens that changes the angle of the terahertz wave that is emitted while the terahertz Farber beam penetrates the object.

The second lens may be a fourth convex lens disposed symmetrically with respect to the third convex lens with respect to an axis perpendicular to the optical axis.

According to the disclosed invention, since the terahertz wave transmitted through the object to be inspected can be condensed with almost no loss, the light condensing efficiency can be increased.

Further, by making the diameter of the terahertz wave beam focused on the object to be inspected be equal to or less than the wavelength of the terahertz wave, a clear image can be obtained by increasing the resolution.

1 is a view for explaining a high resolution inspection apparatus using a vessel beam according to an embodiment of the present invention.
2 is a view for explaining a vessel beam forming unit according to an embodiment of the present invention.
3 is a diagram for calculating the diameter of a terahertz wave beam focused on different vertex angles using Equation (4).
FIGS. 4 and 5 are views for explaining an inspection apparatus for collecting light using a single lens. FIG.
6 is a view for explaining a high-resolution inspection apparatus according to the first embodiment of the present invention.
7 is a view for explaining a high-resolution inspection apparatus according to a second embodiment of the present invention.
8 is a view for explaining a high-resolution inspection apparatus according to the third embodiment of the present invention.
FIGS. 9 and 10 are transmission images obtained by measuring an object to be inspected using the apparatuses of FIGS. 5 to 8. FIG.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a view for explaining a high resolution inspection apparatus using a vessel beam according to an embodiment of the present invention.

Referring to FIG. 1, a high resolution inspection apparatus 100 using a vessel beam includes a terahertz wave generating unit 110, an angle changing unit 120, a vessel beam forming unit 130, an object to be inspected 140, A lens 150, a second lens 160, and a detection unit 170. [

The Bessel beam is a set of Maxwell's equations for free space. It is known as an undiffracted beam. It was introduced for the first time by Durnin in 1987, and has axial symmetry, concentrating energy around the axis like a needle like a certain length. Since it is realized by an optical system having a limited aperture, not an infinite aperture, there is no limitless Beessel beam, which is usually called Quasi-Bessel-Beam (QBB). This QBB can be made of a funnel-shaped lens known as a combination of a hologram, a circular mask with multiple rings or a finite aperture, and a lens, axicon.

The terahertz wave generating unit 110 may generate a terahertz wave. Means an electromagnetic wave in a terahertz blue terahertz range, and preferably has a frequency of 0.1 THz to 10 THz. However, even if the range is somewhat deviated from the above range, it is needless to say that the present invention can be regarded as a terafar insofar as those skilled in the art can easily think of it.

The angle changing unit 120 may change the angle of the terahertz wave incident from the terahertz wave generating unit 110 to be smaller and enter the vessel beam forming unit 130. For example, the angle changing unit 120 may change the incident terahertz wave to a smaller angle or less parallel to the optical axis. The angle changing unit 120 may be a convex lens for refracting the incident terahertz wave in parallel or a parabolic reflector for reflecting the incident terahertz wave in parallel.

The vessel beam forming unit 130 may use a terahertz wave incident from the angle changing unit 120 to form a terahertz wave plasma beam on at least a part of the object to be inspected.

If the angular change unit 120 is not provided, the vessel beam forming unit 130 may use a terahertz wave generated from the terahertz wave generating unit 110 to apply a terahertz wave plasma beam to at least a part of the object to be examined .

Since the vessel beam forming unit 130 is difficult to actually form an ideal vessel beam, the vessel beam formed by the vessel beam forming unit 130 may be called a quasi-bessel beam (QBB). The vessel beam forming structure by the vessel beam forming unit 150 will be described in detail with reference to FIG.

The vessel beam forming unit 130 may be disposed such that a terahertz wave whose angle is changed by the angle changing unit 120 is incident perpendicularly to the incoming surface of the vessel beam forming unit 130.

The vessel beam forming unit 130 may be formed of various types such as a diffractive optical element having a plurality of circular grooves or circular holes, a lens having a positive refractive index, an excitonic lens, or a hologram optical element .

The vessel beam forming unit 130 may be a first axicon lens having a vertex angle such that the diameter of the terahertz wave plasma beam focused on the object is smaller than the wavelength of the terahertz wave generated by the terahertz wave generating unit. have. In this embodiment, the apex angle that forms the diameter of the terahertz Pervasel beam below the wavelength is defined as the maximum apex angle.

In this case, the maximum value of the apex angle τ of the first axicon lens is the Full Width at Half Maximum diameter (ρ _FWHM ) of the terahertz Persell beam focused on the inspection object ), The wavelength?, And the refractive index (n, n ₀ ).

[Equation 1]

가 되어야 하고, 이 값을 만족하는 z=1.1264이다. 이에, 1.1264=k*ρ_FWHM*sinα₀ 식으로부터 위의 수학식 1이 도출될 수 있다. J₀ ²(z)=0.5에서 0.5 값은 변경될 수 있다.In order to satisfy J ₀ ² (z) = 0.5, J ₀ (z) is a first-order Bessel function of J ₀ (z) = 1 /

And z = 1.1264 which satisfies this value. From the equation 1.1264 = k *? _FWHM * sin? ₀ , the above equation 1 can be derived. The value of 0.5 at J ₀ ² (z) = 0.5 can be changed.

&Quot; (2) "

&Quot; (3) "

&Quot; (4) "

Where J _{0 is the} zero order Bessel function

ρ _{FWHM : FWHM of the} focused terahertz Farbessel beam

        λ: wavelength of terahertz wave

α _{0 :} Half value of the crossing angle of the terahertz wave passing through the axicon lens

        n: the refractive index of the first axicon lens

n ₀ : average refractive index of the surrounding environment

        τ: apex angle of the first axicon lens

Equation (4) is a mathematical formula derived using Equations (1), (2) and (3).

On the other hand, the minimum value of the apex angle of the first axicon lens may be the apex angle of the first axicon lens that does not cause total internal reflection according to the refractive index of the first axicon.

Thus, the vertex angle of the first axicon lens having the diameter of the terahertz wave plasma beam formed to be smaller than the wavelength of the terahertz wave generated by the terahertz wave generating unit can be formed between the maximum value and the minimum value as observed above.

The inspection object 140 means an object to be inspected, and may be disposed between the vessel beam forming unit 130 and the first lens 150.

The first lens 150 can change the angle of the terahertz wave generated by the vessel-beam forming unit 130 while transmitting the terahertz laser beam through the object to be examined 140. For example, the first lens 150 can change the angle of the terahertz wave to be less than or equal to a certain angle with respect to the optical axis.

The second lens 160 can condense the terahertz wave that has passed through the first lens 150 to the detector 170.

In the present invention, the high-resolution terahertz wave condensing module means an apparatus including a first lens 150 and a second lens 160. For example, the high-resolution terahertz wave condensing module (first lens and second lens) spreads in the form of a ring-shaped circular beam while moving away from the vessel beam forming unit 130. The high- So that the condensed terahertz wave can be directed to the detection unit 170. [0051]

For example, the high-resolution terahertz wave condensing module may be implemented in various types of configurations such as a convex lens, a concave mirror, a parabolic mirror, an ellipsoidal mirror, and the like.

The detection unit 170 can detect the terahertz wave condensed by the second lens. For example, the detecting section 170 can detect the intensity of the terahertz wave. For example, the detection unit 180 may be implemented with a Schottky diode.

An image generating unit (not shown) may generate a video image using the detected vessel beam. The generated image may be displayed on a display unit (not shown).

The high resolution inspection apparatus using the vessel beam can collect the terahertz wave transmitted through the object to be inspected with almost no loss, thereby increasing the light collection efficiency.

Further, a high resolution inspection apparatus using a vessel beam can obtain a clear image by increasing the resolution by making the diameter of the terahertz wave reaching the detection section to be equal to or lower than the wavelength of the terahertz wave.

2 is a view for explaining a vessel beam forming unit according to an embodiment of the present invention.

Referring to FIG. 2, the vessel beam forming unit may include an axicon (200). R is the radius of the axicon lens, τ is the apex angle of the axicon lens, α ₀ is half of the intersection angle of the beam crossing the axicon lens, and w ₀ is the radius of the parallel light incident on the axicon lens. In addition, the zone in which the vessel beam is formed is indicated by Z _max in FIG. 3, and the terah waves incident on the excimer lens collect energy at the center along the z axis through the constructive interference in this region.

At this time, the Gaussian beam incident on the axicon lens and the vessel beam formed by the axicon lens are distributed in an axial symmetry, and a field is distributed in a circular shape along the z axis. That is, when viewed from the left to the right with reference to FIG. 2, both the Gaussian beam in front of the axicon lens and the vessel beam in the rear of the axicon lens are formed in a circular shape. In particular, the vessel lens formed by the axicon lens is moved away from the axicon lens and spread out into a ring-shaped circular beam.

On the other hand, the most important factor for determining the resolution of an image in a transmitted image obtained by moving a point, such as raster scanning, is the diameter of a beam incident on the object 1 to be inspected.

In particular, in the case of a vessel beam formed by an excitonic lens, its diameter is determined by the wavelength of teraharas and? ₀ , where? ₀ can be obtained by using Snell's law using the following equation (1).

&Quot; (5) "

Here, n ₀ denotes the refractive index in air, n denotes the refractive index of the axicon lens, and τ denotes the apex angle of the axicon lens.

On the other hand, Z _max corresponds to the depth of focus, which can be expressed by the following equation (6).

&Quot; (6) "

Z _max = w ₀ / tan 留₀

Here, w ₀ represents the radius of the beam incident on the axicon lens, as shown in FIG. Referring to these equations, it can be seen that the depth of focus also depends on? ₀ .

Therefore, by combining these points, it can be seen that the resolution and the depth of focus of the image largely change by the value of α ₀ .

2, it is assumed that n ₀ is 1.0, n is 1.54 (High Density Polyethylene), τ is 150 °, R is 25 mm, and α ₀ and the depth of focus Is calculated as follows.

First, when α ₀ is calculated using Equation (5), α ₀ can be calculated to 8.5 °. Further, when the depth of focus (Z _max ) is calculated using Equation (6), Z _max can be calculated as 40.2 mm.

The vessel beam forming portion may include a diffractive optical element in which a plurality of circular grooves or circular holes are arranged concentrically and a lens having a positive refractive index. At this time, the circular grooves or holes formed in the diffractive optical element may be formed in the form of concave plate or through-hole of the diffractive optical element. The lens having such a positive refractive index is arranged opposite to the direction in which the parallel light is incident on the diffractive optical element.

In addition to this embodiment, the vessel beam forming unit may be configured in various forms with a hologram structure or the like.

3 is a diagram for calculating the diameter of a terahertz wave beam focused on different vertex angles using Equation (4).

3, when the wavelength λ of the terahertz wave is 2.14 mm, the refractive index n of the first axicon lens is 1.54, and the average refractive index n ₀ of the surrounding environment is 1, The maximum value of the apex angle? Of the cone lens is about 119 degrees, and the minimum value of the apex angle? Of the first axicon lens is about 99 degrees.

FIGS. 4 and 5 are views for explaining an inspection apparatus for collecting light using a single lens. FIG.

4 and 5, the inspection apparatus 300 includes a terahertz wave generating unit 310, an angle changing unit 320, a vessel beam forming unit 330, a light collecting unit 340, and a detecting unit 350 .

The terahertz wave generating unit 310 may generate a terahertz wave.

The angle changing unit 320 may change the angle of the terahertz wave incident from the terahertz wave generating unit 310 to be smaller and enter the vessel beam forming unit 330.

The vessel beam forming unit 330 may use a terahertz wave incident from the angle changing unit 320 to form a terahertz wave plasma beam on at least a part of the object to be inspected. For example, the vessel beam forming portion may be an excicon. The object to be inspected may be formed between the vessel beam forming unit 330 and the light collecting unit 340.

The light collecting part 340 may be implemented as a single lens.

The detecting unit 350 can detect the terahertz wave condensed by the condensing unit 340.

Referring to FIG. 4, when the apex angle of the axicon, which is the vessel beam forming unit 330, is 140 degrees, the radius of the terahertz wave incident on the detection unit 350 through the object to be inspected is about 5.1 mm, And the terahertz wave diameter at 350 is about 10.2 mm.

In this case, most of the terahertz wave incident from the light collecting part 340 using a single lens has a diameter of about 9 mm and can be condensed by the detecting part 350 having a horn.

Referring to FIG. 5, in order to form the diameter of the terahertz laser beam focused on the object under the wavelength of the terahertz wave, the apical angle of the exciton must be small. In other words, the apex angle of the axicon must be small in order to realize high resolution. Thus, it is formed at 110 degrees smaller than the apex angle of the axicon in Fig.

When the apex angle of the excicon, which is the bemem beam forming unit 330, is 110 degrees, since the radius of the terahertz wave incident on the detection unit 350 through the object to be inspected is about 17 mm, the terahertz The wave diameter is about 34 mm.

As the diameter of the terahertz wave incident on the detection unit 350 increases, only a part of the terahertz wave incident from the light collecting unit 340 using the single lens is condensed by the detection unit 350. In other words, much of the terahertz wave incident from the light collecting portion 340 is not incident on the detecting portion 350, and the detecting performance of the detecting portion 350 is significantly deteriorated.

6 is a view for explaining a high-resolution inspection apparatus according to the first embodiment of the present invention.

6, the high resolution inspection apparatus 500 includes a terahertz wave generating unit 510, an angle changing unit 520, a vessel beam forming unit 530, a first lens 540, a second lens 550, And a detection unit 560.

The terahertz wave generating unit 510 may generate a terahertz wave.

The angle changing unit 520 may change the angle of the terahertz wave incident from the terahertz wave generating unit 510 to be smaller and enter the vessel beam forming unit 530.

The vessel beam forming unit 530 may use a terahertz wave incident from the angle changing unit 520 to form a terahertz perse beam on at least a part of the object to be inspected. For example, the vessel beam forming portion may be an excicon.

The object to be inspected may be formed between the vessel lens forming unit 530 and the first lens 540.

The vessel beam forming unit 530 may be a first axicon lens having a vertex angle in which the diameter of the terahertz wave plasma beam is smaller than the wavelength of the terahertz wave generated in the terahertz wave generating unit.

The maximum value of the apex angle of the first axicon lens can be calculated based on Equations (1) to (3). For example, when the wavelength λ of the terahertz wave is 2.14 mm, the refractive index n of the first axicon lens is 1.54, and the average refractive index n ₀ of the surrounding environment is 1, Has a value of about 119 degrees. Thus, the maximum value of the apex angle of the first axicon lens is about 119 degrees.

On the other hand, the minimum value of the first X-con lens may be a vertex angle of the first X-axis lens that does not cause total internal reflection according to the refractive index of the first axicon. With respect to the refractive index in this embodiment, the critical angle due to total reflection is 99 degrees. Therefore, the minimum value of the twist angle of the first axicon lens is about 99 degrees.

Finally, if the vertex angle of the first axicon lens is formed between 119 degrees, which is the maximum value, and 99 degrees, which is the minimum value, the diameter of the terahertz wavelength laser beam is smaller than the wavelength of the terahertz wave generated by the terahertz wave generator do.

The first lens 540 can change the angle of the terahertz wave generated by the vessel-beam forming unit 530 to be transmitted while passing through the object to be examined.

The first lens 540 may be a second axicon lens arranged symmetrically with respect to the first axicon lens 530 on the basis of the object to be inspected.

The second axicon lens 550 may have an apex angle that is the same as that of the first axicon lens 530. In this case, the size of the second axicon lens may be smaller than or equal to the size of the first axicon lens 530. [ When the apex angle of the second axicon lens is the same as that of the first axicon lens 530, the efficiency with which the terahertz wave is condensed by the detection unit 550 is the best.

If the angle changing unit 520 is a first convex lens, the second lens 550 may be a second convex lens arranged symmetrically with respect to the first convex lens with respect to the object to be inspected.

When the wavelength? Of the terahertz wave is 2.14 mm and the first axicon lens of the vessel beam forming unit 530 is 110 degrees, since the radius of the terahertz wave in the detector 560 is 0.006 mm, The diameter of the wave is 0.012 mm.

The terahertz wave condensed by the detector 560 is condensed by the detector 350 in Figure 5 so that the diameter of the terahertz wave condensed by the detector 560 is converged by the first lens 540 and the second lens 550. [ The condensing efficiency can be increased.

Accordingly, when the first lens 540 and the second lens 550 are used to condense the terahertz wave, even when the vertex angle of the first axicon lens is small, the high condensing efficiency can be obtained and the resolution can be remarkably increased, A test image can be obtained.

7 is a view for explaining a high-resolution inspection apparatus according to a second embodiment of the present invention.

7, the high resolution inspection apparatus 600 includes a terahertz wave generating unit 610, an angle changing unit 620, a vessel beam forming unit 630, an object to be inspected 640, a first lens 650, A second lens 660, and a detection unit 670.

The terahertz wave generating unit 610 may generate a terahertz wave.

The angle changing unit 620 may change the angle of the terahertz wave incident from the terahertz wave generating unit 610 to be smaller and enter the vessel beam forming unit 630.

The vessel beam forming unit 630 may use a terahertz wave incident from the angle changing unit 620 to form a terahertz wave plasma beam on at least a part of the object to be inspected. For example, the vessel beam forming portion may be an excicon.

The object to be inspected may be formed between the vessel beam forming portion 630 and the light collecting portion 640.

The vessel beam forming unit 630 may be a first axicon lens having a vertex angle in which the diameter of the terahertz wave plasma beam is smaller than the wavelength of the terahertz wave generated in the terahertz wave generating unit.

The first lens 640 may be a third convex lens that changes the angle of the terahertz wave that is emitted while the terahertz laser beam passes through the object to be inspected.

The second lens 650 may be a fourth convex lens disposed symmetrically with respect to the third convex lens with respect to an axis perpendicular to the optical axis.

When the wavelength? Of the terahertz wave is 2.14 mm, the radius of the terahertz wave incident on the detector 660 through the object to be inspected is about 2.5 mm, so that the diameter of the terahertz wave in the detector is about 5 mm .

By condensing the terahertz wave using the first lens 640 and the second lens 650, the light condensing efficiency can be increased by significantly reducing the diameter of the terahertz wave condensed by the detector 350 in Fig. Thus, the high resolution inspection apparatus according to the present embodiment can achieve a high condensation efficiency even when the apex angle of the first axicon lens is small, and can remarkably increase the resolution, thereby obtaining a high-resolution inspection image.

8 is a view for explaining a high-resolution inspection apparatus according to the third embodiment of the present invention.

8, the high resolution inspection apparatus 700 includes a terahertz wave generating unit 710, an angle changing unit 720, a vessel beam forming unit 730, an object to be inspected 740, a first lens 750, A second lens 760, and a detection unit 770.

The terahertz wave generating unit 710 may generate a terahertz wave.

The angle changing unit 720 may change the angle of the terahertz wave incident from the terahertz wave generating unit 710 to be smaller and enter the vessel beam forming unit 730.

The vessel beam forming unit 730 may use a terahertz wave incident from the angle changing unit 720 to form a terahertz Pervasell beam on at least a part of the object to be inspected. For example, the vessel beam forming portion may be an excicon.

The object to be inspected may be formed between the vessel beam forming unit 730 and the light collecting unit 740.

The vessel beam forming unit 730 may be a first axicon lens having a vertex angle in which the diameter of the terahertz wave plasma beam is smaller than the wavelength of the terahertz wave generated in the terahertz wave generating unit.

The first lens 740 may be a second axicon lens arranged symmetrically with respect to the first axicon lens 730 on the basis of the object to be inspected.

The second axicon lens may have an apex angle equal to that of the first axicon lens 730. [

The second lens 750 has the same shape as the second axicon lens 740 and may be arranged symmetrically with respect to the second axicon lens 740 with respect to an axis perpendicular to the optical axis.

When the wavelength? Of the terahertz wave is 2.14 mm, the radius of the terahertz wave transmitted through the object to be examined and entering the detection unit 760 is about 1.7 mm. Therefore, the diameter of the terahertz wave in the detection unit 760 About 3.4 mm.

By condensing the terahertz wave using the first lens 740 and the second lens 750, the condensing efficiency can be increased by significantly reducing the diameter of the terahertz wave condensed by the detector 350 in Fig. Thus, the high resolution inspection apparatus according to the present embodiment can achieve a high condensation efficiency even when the apex angle of the first axicon lens is small, and can remarkably increase the resolution, thereby obtaining a high-resolution inspection image.

FIGS. 9 and 10 are transmission images obtained by measuring an object to be inspected using the apparatuses of FIGS. 5 to 8. FIG.

Specifically, FIG. 9 shows the measurement of an object to be inspected using the apparatus described with reference to FIG. 5, and FIG. 10 shows an object to be inspected using the apparatus described with reference to FIGS. 6 to 8.

Referring to FIG. 9, it can be confirmed that the object to be inspected can not be discriminated at all with the transmitted image obtained by focusing with only a single lens.

On the other hand, referring to FIG. 10, it can be seen that the object to be inspected can be clearly identified by the transmission image obtained by collecting light in the lens configuration of FIGS. 6 to 8. FIG.

As described above, a high resolution image can be obtained by using a high resolution inspection apparatus using a vessel beam according to the present invention.

The embodiments described may be constructed by selectively combining all or a part of each embodiment so that various modifications can be made.

It should also be noted that the embodiments are for explanation purposes only, and not for the purpose of limitation. In addition, it will be understood by those of ordinary skill in the art that various embodiments are possible within the scope of the technical idea of the present invention.

100: High-resolution inspection system using vessel beam
110: terahertz wave generating unit
120: Angle changing portion
130: Bezel beam forming section
140: object to be inspected
150: first lens
160: Second lens
170:

Claims (18)

A terahertz wave generating unit for generating a terahertz wave;
Wherein the terahertz wave plasma beam is formed on the object to be inspected using the terahertz wave incident from the terahertz wave generating unit, and the diameter of the terahertz wave plasma beam is larger than the terahertz wave generated by the terahertz wave generating unit A Bezel beam forming unit that is a first axicon lens having a vertex angle smaller than the wavelength of the Bezel beam;
A first lens for changing the angle of the terahertz wave radiated from the terahertz laser beam while passing through the object to be inspected;
A second lens for converging the terahertz wave having passed through the first lens to a detector; And
And a terahertz wave detecting unit for detecting the terahertz wave condensed by the second lens.
delete The method according to claim 1,
Wherein the maximum value of the apex angle of the first axicon lens

Where J _{0 is the} zero order Bessel function
ρ _{FWHM: FWHM of the} focused terahertz Farbessel beam
λ: wavelength of terahertz wave
α _0: Half value of the crossing angle of the terahertz wave passing through the axicon lens
n: the refractive index of the first axicon lens
n ₀ : average refractive index of the surrounding environment
τ: apex angle of the first axicon lens
Which is the apex angle? Of the first axicon lens calculated through the above equation, using a Bezel beam.
The method according to claim 1,
Wherein the minimum value of the apex angle of the first axicon lens
Wherein the first axial lens is a vertex angle of the first axial lens which does not cause total internal reflection due to the refractive index of the first axial lens.
The method according to claim 1,
Wherein the first lens comprises:
And a second axicon lens disposed symmetrically with respect to the first axicon lens based on the object to be inspected.
6. The method of claim 5,
The second axicon lens includes a first lens,
And a vertex angle of the same magnitude as that of the first axicon lens.
The method according to claim 1,
Further comprising an angle changing unit for changing the angle of the terahertz wave incident from the terahertz wave generating unit to be smaller and entering the vessel beam forming unit.
6. The method of claim 5,
Further comprising an angle changing unit that is a first convex lens for changing the angle of the terahertz wave incident from the terahertz wave generating unit to be incident on the vessel beam forming unit,
And the second lens comprises:
And a second convex lens disposed symmetrically with respect to the first convex lens on the basis of the object to be inspected.
6. The method of claim 5,
And the second lens comprises:
And a third exicon lens having the same shape as the second exicon lens and arranged symmetrically with respect to the second exicon lens with respect to an axis perpendicular to the optical axis.
The method according to claim 1,
Wherein the first lens comprises:
And a third convex lens that changes the angle of the terahertz wave that is emitted while the terahertz Farber beam penetrates the object to be inspected.
11. The method of claim 10,
And the second lens comprises:
And a fourth convex lens arranged symmetrically with respect to the third convex lens with respect to an axis perpendicular to the optical axis.
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