KR101107853B1 - Imaging device for terahertz single-pixel diffraction image - Google Patents

Abstract

PURPOSE: A terahertz single pixel diffraction video device is provided to obtain 2D image of a subject without a separate measuring device like CCD. CONSTITUTION: A terahertz single pixel diffraction video device comprises a phase delay device(120) and a terahertz beam measuring unit(150). The phase-delaying device is arranged in the front or rear side of an object material(130). The phase-delaying device refracts a terahertz beam(110). The terahertz beam is researched to the object material. The terahertz beam measuring unit measures the phase-delaying device and terahertz beam in two dimensions. The terahertz beam is refracted with the object material. The terahertz beam measuring unit locates in the spatial frequency domain.

Description

Terahertz Single Pixel Diffraction Imaging Device {IMAGING DEVICE FOR TERAHERTZ SINGLE-PIXEL DIFFRACTION IMAGE}

The following embodiment relates to a terahertz single pixel diffraction imaging apparatus using a terahertz beam, and more particularly, to a terahertz single pixel diffraction imaging apparatus which reconstructs a 2D image of a target object using the terahertz beam as a light source.

The diffraction image method generally refers to a technique of obtaining an image of an original object by irradiating a light source having a strong coherence to the object, measuring a pattern of the light source when the irradiated light source is diffracted, and performing Fourier analysis. Since the pattern of the diffracted light source can be represented in two dimensions, a conventional diffractive imaging apparatus generally uses a measuring device which is composed of an array or a charge-coupled device (CCD).

However, in the case of a measuring device implemented with an array or a CCD, due to the high price of the measuring device, the price of the diffractive imaging device may also increase.

In particular, the field of applying the terahertz light source has recently been in the spotlight, and in a diffractive imaging device using the terahertz light source, mounting a costly array or a measuring device implemented with a CCD may become inefficient. Can also be complicated.

According to an embodiment of the present invention, a terahertz single pixel diffraction imaging apparatus capable of reconstructing a 2D image by refraction of a spectrum of a terahertz beam irradiated onto a target object using a terahertz beam as a light source and using a phase delay device to provide.

In addition, according to an embodiment of the present invention, the spectrum of a wide region of the terahertz beam can be refracted at the same angle using a phase delay device, and a 2D image of the target object can be imaged using a single pixel terahertz measuring device. There is provided a terahertz single pixel diffraction imaging device.

According to an embodiment of the present invention, a terahertz single pixel diffraction imaging apparatus includes a phase retarder disposed in front of or behind a target object and refracting the terahertz beam irradiated toward the target object, the phase delay device and the target object. It includes a terahertz beam measuring unit for measuring the terahertz beam refracted by two-dimensional.

The terahertz single pixel diffraction imaging apparatus may further include a lens positioned at a focal length with respect to the target object to generate a spatial frequency domain of the target object, and the terahertz beam measuring unit may be configured to generate the spatial frequency domain. It can be located at

In addition, the phase retardation apparatus can refract the spectrum of the wide region of the terahertz beam at the same angle.

In addition, the phase delay device may be a wedge-shaped optical component.

The terahertz beam measuring unit may be positioned in the center of the spatial frequency domain of the target object, and may be a terahertz single pixel measuring device.

In addition, the terahertz beam measuring unit inverse Fourier transform and inverse to the terahertz beam refracted by the phase delay device and the target object based on the one-dimensional time data set obtained by rotating the phase delay device at a predetermined angle A radon transform may be applied to obtain a 2D image of the target object.

The 2D image of the target object may have a feature similar to a circular shape of the target object as the number of angles of rotating the phase delay device for obtaining the one-dimensional time data set increases.

In addition, the terahertz beam measuring unit may be a semiconductor device or a photoconductive antenna for all-optical sampling.

According to another embodiment of the present invention, a terahertz single pixel diffraction imaging apparatus may include a phase delay device disposed in front of or behind a target object and refracting the terahertz beam irradiated toward the target object, and a focal length with respect to the target object. And a parabolic mirror reflecting the terahertz beam refracted by the phase delay device and the target object, and a terahertz beam measuring unit measuring two-dimensionally the terahertz beam reflected by the parabola mirror.

In this case, the terahertz single pixel diffraction imaging apparatus may further include a pellicle beam splitter between the parabolic mirror and the terahertz beam measuring unit.

The terahertz single pixel diffraction imaging apparatus according to another embodiment of the present invention is disposed in front of or behind a target object, and a phase delay device for refracting the terahertz beam irradiated toward the target object and a far field approximation (Far Field). And a terahertz beam measuring unit disposed at a position satisfying an approximation condition and measuring terahertz two-dimensionally refracted by the phase delay device and the target object.

According to an embodiment of the present invention, by terminating a terahertz beam having a broad spectrum spectrum using a phase delay device, a two-dimensional image of a target object can be obtained without using a multi-measuring device such as a CCD. Accordingly, the unit cost of the beam measuring instrument can be lowered and the installation surface can be simplified.

1 is a view showing the configuration of a terahertz single pixel diffraction imaging apparatus according to an embodiment of the present invention.
FIG. 2 is a side view geometrical representation of the phase delay device shown in FIG. 1; FIG.
3 illustrates a terahertz single pixel diffraction imaging apparatus according to another embodiment of the present invention.

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

The terahertz single pixel diffraction imaging apparatus according to the embodiment of the present invention is an imaging apparatus for a terahertz single pixel diffraction image, which uses a broad band spectrum of terahertz. The device reconstructs two-dimensional images using light pulses of terahertz electromagnetic waves with a broad spectrum of spectrum that maintains coherence

1 is a view showing the configuration of a terahertz time domain spectroscopy apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the terahertz single pixel diffraction imaging apparatus 100 is generated by a real domain in which an object 130 to be imaged is placed and a lens 140 disposed behind the object 130. It has a spatial frequency domain (spatial frequency domain).

The terahertz beam 110 has an optical pulse for obtaining a terahertz time domain spectroscopic image. For example, the terahertz beam 110 may be a femto second optical pulse laser.

The terahertz single pixel diffraction imaging apparatus 100 uses the terahertz beam 110 as a light source to acquire a 2D image of a target object, and transmits the phase delay device 120 and The terahertz beam measuring unit 150 is disposed.

In more detail, the phase delay device 120 is disposed in front of or behind the object 130, and the beam measuring unit 150 is located at the center of the spatial frequency domain corresponding to the object 130.

Accordingly, the terahertz beam 110 is diffracted past the phase delay device 120 and the target object 130, and passes through the lens 140 to the terahertz beam measuring unit 150. Since the terahertz beam 110 can measure two-dimensionally the terahertz beam 110 as it is refracted by the phase retarder 120, the single-pixel terahertz measuring device 150 can be measured. It can be implemented as.

2 is a diagram illustrating the phase delay device 120 in terms of geometry.

Referring to FIG. 2, the phase retarder 200 is a slanted phase retarder and obliquely refracts the terahertz beam. In particular, the phase retarder 200 is a wedge-shaped optical component. Can be implemented.

라면, 위상 지연 장치(200)의 굴절시키는 각

은 스넬의 법칙에 따라 아래의 수학식 1과 같이 나타낼 수 있다.If the refractive index of the phase delay device 200 is n, the angle between

If it is, the angle of refraction of the phase delay device 200

Can be expressed as Equation 1 below according to Snell's law.

[Equation 1]

의 값에도 오차가 발생할 수 있다그러나, 위상 지연 장치(200)는 테라헤르츠 빔을 굴절시켜 실제 도메인(x,y)에 위상 지연 효과를 줄 수 있다는 점이 중요하다이러한 효과는 아래의 수학식 2와 같이 나타낼 수 있다.At this time, the geometry of the phase delay device 200 may have an error in the actual design, so

However, it is important that the phase delay device 200 bends the terahertz beam to give a phase delay effect on the actual domain (x, y). Can be represented as:

[Equation 2]

는 광원의 파수(wave number)이며,

는 위상 지연 장치(200)의 방위각을 나타낸다이때, 위상 지연 효과는 위상 지연 장치(200)를 대상 물체 뒤에 두어도 나타나는 것이므로, 위상 지연 장치(200)를 반드시 대상 물체 앞에 둘 필요는 없다.here,

Is the wave number of the light source,

Denotes an azimuth angle of the phase retarder 200. Since the phase retardation effect appears even when the phase retarder 200 is placed behind the target object, it is not necessary to place the phase retarder 200 before the target object.

The refractive index of the phase retardation device 200 needs to be substantially constant in the spectrum of a wide region of the terahertz beam. Thus, the material of the phase retardation device 200 may be made of high-resistance silicon, teblon, or the like.

은 아래의 수학식 3과 같이 나타낼 수 있다.Due to this phase delay effect, the spectrum of the terahertz beam measured in a terahertz single pixel diffraction imaging device

May be expressed as Equation 3 below.

&Quot; (3) "

는 광원의 각도 주파수(angular frequency)를 나타내고,

는 테라헤르츠 빔의 스펙트럼 정보를 나타내고,

는 영상화하고자 하는 대상 물체의 함수이다따라서, 퓨리에 단면 정리(Fourier slice theorm)에 따르면, 수학식 3에 의해 측정되는

는

의

방향으로 방사형의 형태로 투영하여 얻는 1D 시노그램(sonogram) 정보의 퓨리에 변환과 일치하게 된다따라서, 본 발명에서 테라헤르츠 빔처럼 넓은 영역의 스팩트럼을 갖는 상황에서는 스펙트럼에 따른 신호가 1D 시노그램 정보의 퓨리에 변환된 공간 주파수에 일대일로 대응될 수 있다따라서,

에 퓨리에 역변환을 적용하면,

방향으로 방사형의 형태로 투영된 1D 시노그램을 알 수 있다.here,

Denotes the angular frequency of the light source,

Represents the spectral information of the terahertz beam,

Is a function of the object to be imaged, and according to Fourier slice theorm,

Is

of

In accordance with the Fourier transform of 1D sonogram information obtained by projecting in a radial form in the direction, according to the present invention, a signal according to a spectrum is obtained in a situation in which the spectrum has a large area such as a terahertz beam. Can correspond to the Fourier transformed spatial frequency one-to-one.

Applying a Fourier inverse to

The 1D sinogram projected in a radial form in the direction can be seen.

Using this principle, the terahertz single pixel diffraction imaging apparatus measures the signal by rotating the phase delay apparatus 200 at an angle unit from 0 degree to 180 degrees, and then acquires a set of 1D time data projected in all directions. In addition, as the inverse Radon transformation is applied, the image of the target object may be restored. In this case, as the number of angles for rotating the phase retardation apparatus 200 increases, that is, in a more dense angle unit than before. As the measurement is performed, an image closer to the prototype of the object may be obtained. This process may be represented by Equation 4 below.

&Quot; (4) "

3 is a diagram illustrating a terahertz single pixel diffraction imaging apparatus 300 according to another exemplary embodiment of the present invention.

Referring to FIG. 3, the terahertz beam 310 is first diffracted through the phase delay device 320 and the target object 330, and the diffracted terahertz beam 310 is applied to the parabola mirror 340. It is transmitted to the terahertz beam measuring unit 350 by.

In this case, the parabola mirror 340 is used instead of the lens shown in FIG. 1, and the terahertz single pixel diffraction imaging apparatus 300 uses the pellicle beam splitter 360 to parabola mirror 340 and the terahertz beam measuring unit 350. Can be placed between

Since the pellicle beam splitter 360 transmits terahertz and reflects near infrared rays, the pellicle beam splitter 360 may transmit a near-infrared ray (NIR) pulse to the terahertz beam measuring unit 350. In addition, the terahertz beam measuring unit 350 may measure the terahertz beam 310 by an electro-optical sampling method.

In this case, the terahertz beam measuring unit 350 used ZnTe, which is a semiconductor device for all-optical sampling of the terahertz beam according to an embodiment of the present invention, the present invention is not limited to this, a photoconductive antenna , PCA) may be used.

In addition, the parabola mirror 340 is arranged to reliably define the spatial frequency domain in which the diffraction pattern is expressed as a Fourier transform, however, other embodiments of the present invention may use a Far Field Approximation condition. That is, if the measurement of the terahertz beam measuring unit 350 is made under a distance approximation condition, the parabolic mirror 340 or the lens illustrated in FIG. 1 may not be disposed. Here, the distance approximation is a terahertz beam 310. In the case of measuring a long distance compared to the wavelength of the target object and the terahertz beam 310 to diffract), it means that the diffraction pattern is represented by the Fourier transform of the object.

As a result, the terahertz single pixel diffraction imaging apparatus of the present invention includes a phase delay apparatus and a terahertz beam measuring unit, wherein the phase delay apparatus is disposed in front of or behind the object, and radiates the terahertz beam irradiated toward the object. And the terahertz beam measuring unit measures two-dimensionally the terahertz beam refracted by the phase retardation device and the target object, wherein the terahertz beam measuring unit is located at a focal length with respect to the target object, A lens for generating a domain may be further included, and the terahertz beam measuring unit may be located in the generated spatial frequency domain. The phase retardation apparatus may refract the spectrum of a wide region of the terahertz beam at the same angle. The phase delay device may be a wedge-shaped optical component. The terahertz beam side The unit is located in the center of the spatial frequency domain of the target object, and may be a terahertz single pixel measuring device, and the terahertz beam measuring unit is based on a one-dimensional time data set obtained by rotating the phase delay device at an angle. The 2D image of the target object may be obtained by applying an inverse Fourier transform and an inverse radon transform to the terahertz beam refracted by the phase delay device and the target object. The greater the number of angles for rotating the phase delay device to obtain a set, the more similar to the circular shape of the target object. The terahertz beam measuring unit may be a semiconductor device or a photoconductive antenna for all-optical sampling.

The terahertz single pixel diffraction imaging apparatus includes: a phase delay device disposed in front of or behind a target object and refracting the terahertz beam irradiated toward the target object; A parabolic mirror positioned at a focal length with respect to the object and reflecting the terahertz beam refracted by the phase delay device and the object; And a terahertz beam measuring unit measuring two-dimensionally the terahertz beam reflected by the parabola mirror. A pellicle beam splitter may be further disposed between the parabola mirror and the terahertz beam measuring unit. A phase delay device disposed in front of or behind the beam, and refracting the terahertz beam irradiated toward the object; And a terahertz beam measuring unit disposed at a position satisfying a far field approximation condition and measuring two-dimensional terahertz refraction by the phase delay device and the target object.

The terahertz single pixel diffraction imaging apparatus includes: a phase delay device disposed in front of or behind a target object and refracting the terahertz beam irradiated toward the target object; And a terahertz beam measuring unit disposed at a position satisfying a far field approximation condition and measuring terahertz two-dimensionally refracted by the phase delay device and the target object.

Method according to an embodiment of the present invention is implemented in the form of program instructions that can be executed by various computer means may be recorded in a computer readable medium. The computer readable medium may be a program command, a data file, a data structure alone The program instructions recorded on the media may be those specially designed and constructed for the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

Claims (11)

A phase delay device disposed in front of or behind the object and refracting the terahertz beam irradiated toward the object; And
A terahertz beam measuring unit measuring two-dimensionally the terahertz beam refracted by the phase delay device and the target object
Terahertz single pixel diffraction imaging device comprising a. The method of claim 1,
A lens positioned at a focal length with respect to the target object to generate a spatial frequency domain of the target object,
The terahertz beam measuring unit is located in the generated spatial frequency domain
Terahertz single pixel diffraction imaging device. The method of claim 1,
The phase delay device
Refracting the broad spectrum of the terahertz beam at the same angle
Terahertz single pixel diffraction imaging device. The method of claim 1,
The phase delay device is a wedge-shaped optical component
Terahertz single pixel diffraction imaging device. The method of claim 1,
The terahertz beam measuring unit
Located in the center of the spatial frequency domain of the target object, a terahertz single pixel measurement device
Terahertz single pixel diffraction imaging device. The method of claim 5,
The terahertz beam measuring unit
The inverse Fourier transform and the inverse radon transform are applied to the terahertz beam refracted by the phase delay device and the target object based on the one-dimensional time data set obtained by rotating the phase delay device at an angle. To acquire 2D images of
Terahertz single pixel diffraction imaging device. The method of claim 6,
The 2D image of the target object
The larger the number of angles for rotating the phase delay device for obtaining the one-dimensional time data set, the more similar to the circular shape of the target object.
Terahertz single pixel diffraction imaging device. The method of claim 1,
The terahertz beam measuring unit
Semiconductor devices or photoconductive antennas for all-optical sampling
Terahertz single pixel diffraction imaging device. A phase delay device disposed in front of or behind the object and refracting the terahertz beam irradiated toward the object;
A parabolic mirror positioned at a focal length with respect to the object and reflecting the terahertz beam refracted by the phase delay device and the object; And
A terahertz beam measuring unit measuring two-dimensionally the terahertz beam reflected by the parabolic mirror
Terahertz single pixel diffraction imaging device comprising a. 10. The method of claim 9,
Placing a pellicle beam splitter between the parabolic mirror and the terahertz beam measuring unit
Terahertz single pixel diffraction imaging device. A phase delay device disposed in front of or behind the object and refracting the terahertz beam irradiated toward the object; And
A terahertz beam measuring unit disposed at a position satisfying a far field approximation condition and measuring terahertz two-dimensionally refracted by the phase delay device and the target object.
Terahertz single pixel diffraction imaging device comprising a.

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