KR20110050812A - Measuring apparatus using terahertz wave - Google Patents

Abstract

PURPOSE: An object inspecting apparatus using terahertz wave is provided to enable a user to obtain high quality images from phase information when reading images by amplitude information is difficult. CONSTITUTION: An object inspecting apparatus using terahertz wave comprises a transmitter(10), a receiver(20), a reference signal generator(30), a lock-in amplifier(40), and an analysis apparatus(50). The transmitter generates terahertz wave and makes terahertz wave incident to a specimen(1). The receiver receives terahertz waves and outputs intermediate frequency signals as measurement signals. The reference signal generator converts the signal inputted to the transmitter and the receiver and generates reference signals. The lock-in amplifier receives the measurement signals of the receiver and reference signals of the reference signal generator. The lock-in amplifier outputs amplitude signals and phase signals. The analysis apparatus analyzes identity information of an object using one or both of the amplitude signal and the phase signal.

Description

Object inspection device using terahertz waves {Measuring Apparatus using Terahertz Wave}

The present invention relates to an apparatus for inspecting an object, and more particularly, to an apparatus for measuring characteristics such as transmittance or generating an image of an object by using a terahertz wave.

Today, applications using terahertz (THz) waves, or electromagnetic waves in terahertz frequency units, have attracted much attention worldwide.

The terahertz wave generally has a frequency range of 0.1 THz to 10 THz, and as such frequency range is located in the middle of the radio wave and the light wave, the terahertz wave has the advantage of simultaneously maintaining the transmittance of the radio wave and the straightness of the light wave.

In addition, the terahertz wave energy has a characteristic of causing resonance of most molecules, such as torsion, vibration, rotational energy, etc., so that the characteristic can identify the unique absorption spectrum inherent in the material.

Recently, applications using terahertz wave characteristics in spectroscopy and imaging have been actively studied.

In general, a method for generating terahertz waves includes a method using an optical device such as a laser (Ref. [1]).

When using optical devices, a wide frequency spectrum can be obtained, which can be used to obtain the material's intrinsic absorption spectrum (Ref. [2]), depth and range information (Ref. [3]. ]) Has the advantage of obtaining a wide range of information of the object, such as, but it takes a long time to measure the sample, the size of the device in the actual configuration, as well as the installation cost is high.

This drawback is a fatal weakness in the field of imaging research aimed at real-time nondestructive testing of objects.

As a source for imaging, terahertz waves have a shorter wavelength than traditional microwaves, so they have very good spatial resolution and can penetrate almost any object except water and metal.

In addition, it has the advantage of being harmless to the human body because it has a very low energy than x-ray (ray), γ-ray currently used in various applications in the field of medicine, security and the like.

This is one of the reasons why terahertzpa has attracted worldwide attention in the field of imaging recently (Refs. [4], [5]), and it is known that it can be applied to various technical fields such as explosive detection and cancer cell diagnosis. .

[references]

[1] Martin van Exter and D. Grischkowsky, "Characterization of an optoelectronic terahertz beam system," IEEE Transactions on Microwave Theory and Techniques. vol. 38, pp. 1684-1691, 1990.

[2] Chen Y, Liu H, Deng Y, Veksler D, Shur M and Zhang X-C “Spectroscopic characterization of explosives in the far infrared region,” SPIE Defense and Security Symp. # 5411-2, 2004.

[3] McClatchey K, Reiten M T and Cheville R A. “Time resolved synthetic aperture terahertz impulse imaging,” Appl. Phys. Lett. vol. 79, pp. 4485-4487, 2001.

[4] S. Nakajima, H. Hoshina, M. Yamashita and C. Otani, “Terahertz imaging diagnostics of cancer tissues with a chemometrics technique,” Appl. Phys. Lett. vol. 90, 041102, 2007.

[5] DT Petkie, C. Casto, FCD Lucia, SR Murrill, B. Redman, RL Espinola, CC Franck, EL Jacobs, ST Griffin, CE Halford, J. Reynolds, S. O 'Brien and D. Tofsted, “ Active and passive imaging in the THz spectral region: phenomenology, dynamic range, modes, and illumination, ”J. Opt. Soc. Am. B. vol. 25, pp. 1523-1531, 2008.

However, when using the terahertz wave as described above, it is necessary to reduce the size of the device and to obtain excellent imaging results, and to develop an apparatus capable of improving the accuracy of measurement results and shortening the measurement time.

Therefore, the present invention has been invented in view of the above, and an object thereof is to provide a compact inspection apparatus having a simpler configuration based on an electrical apparatus.

In addition, the present invention can reduce the cost of manufacturing the device to reduce the manufacturing cost, and to provide a compact real-time terahertz imaging device that can obtain excellent imaging results with a reduction in measurement time and measurement accuracy There is this.

In order to achieve the above object, the present invention comprises a transmitter for generating a terahertz wave incident on the specimen; A receiver which receives the terahertz wave incident from the transmitter and passes through the object and outputs the measured signal modulated into an IF signal; A reference signal generator for converting a signal input from the transmitter and the receiver to generate a reference signal; A lock-in amplifier receiving the measurement signal of the receiver and the reference signal of the reference signal generator and outputting an amplitude signal and a phase signal detected from the measurement signal; Provided is an object inspection apparatus using a terahertz wave comprising an analysis device for analyzing the unique information of the specimen using at least one of the amplitude signal and the phase signal collected from the lock-in amplifier.

Accordingly, according to the object inspection apparatus using the terahertz wave according to the present invention, it is possible to reduce the size of the device compared to the conventional, excellent imaging results, improved accuracy of measurement results and shorter measurement time is possible This will be.

In particular, it is possible to miniaturize the device by eliminating the need for a huge femto-second laser like the conventional inspection device, and it is necessary to align the existing device because it is composed of only the electronic device. In addition, the compact device configuration is possible with only small components, so the configuration can be easily changed as necessary.

In addition, it is possible to reduce the cost of device configuration, thereby reducing manufacturing costs, reducing measurement time, and simultaneously using phase and amplitude information to obtain excellent imaging results. At the same time, the accuracy of the measurement results is improved. Conventionally, since only amplitude information obtained from a target object is used for imaging, when accurate reading of the image obtained with only the amplitude information is impossible, accurate measurement results are not known. However, in the present invention, phase information may be used, and thus only the amplitude information may be used. If it is difficult to read, a better image can be obtained from the phase information.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

The present invention relates to a compact terahertz wave inspection apparatus capable of miniaturization, excellent imaging results, improved measurement results, shorter measurement time, and reduced manufacturing cost.

In particular, the present invention uses a transmitter (Terahertz Transmitter; THz Tx) and a receiver (Terahertz Receiver (THz Rx)) based on the electrical device, injecting a terahertz electromagnetic wave to the specimen (object to be tested) at the same time The main focus is on receiving terahertz electromagnetic waves transmitted through water and enabling imaging in real time on an object based on amplitude and phase information obtained therefrom.

That is, in the present invention, as a real-time non-destructive measuring device of the object through terahertz imaging, a method for enabling a quick measurement and to simplify the device configuration and miniaturization, and to lower the manufacturing cost of the device, Electronic devices such as diodes, oscillators, and frequency multipliers are used.

At this time, a terahertz wave (eg, 336.168 GHz ≒ 0.34 THz) of a predetermined frequency is generated using a phase locked DRO (Dielectric Resonator Oscillator) and a transmitter including a multiplier, and a Schottky diode detector (receiver) Inherent amplitude and phase information can be obtained from the measured signal.

As an embodiment of the present invention, for the implementation of a compact terahertz imaging device, the transmitter may be configured to generate and output electromagnetic waves of 0.34 THz as described below, and further, the electromagnetic waves of 0.34 THz generated by the transmitter. The apparatus may be configured to receive a receiver and to measure amplitude and phase information of the object under test.

The object inspection apparatus of the present invention can be usefully used for performing a quick and easy real-time terahertz nondestructive inspection in various fields such as medical, security, space, and communication.

This configuration of the present invention will be described in more detail.

1 is a schematic diagram showing the overall configuration of an object inspection apparatus according to the present invention composed of a terahertz imaging device, Figure 2 is a block diagram showing the configuration of a transmitter in the object inspection apparatus according to the present invention, Figure 3 A block diagram showing the configuration of a receiver in the object inspection apparatus according to the present invention.

4 is a block diagram showing the configuration of the reference signal generator in the object inspection apparatus according to the present invention, Figure 5 is a block diagram schematically showing the overall configuration of the object inspection apparatus according to the present invention.

First, the object inspection apparatus using the terahertz wave of the present invention comprises a transmitter (Tx) 10 that generates a terahertz wave of a predetermined frequency and enters the specimen (sample) 1 from the transmitter 10. A receiver (Rx) 20 which receives a terahertz wave incident and transmitted through the specimen 1 and outputs it as a measurement signal of a predetermined frequency band modulated into an IF signal, and in the transmitter 10 and the receiver 20 The reference object generator 30 converts an input signal to generate a reference signal of a predetermined frequency band, and processes the reference signal of the reference signal generator 30 and the measurement signal of the receiver 20 to process the test object 1. A lock-in amplifier 40 for outputting an amplitude signal and a phase signal representing the unique information to be possessed, and an analyzer 50 for analyzing and processing the amplitude and phase signals collected through the lock-in amplifier 40. It is configured to include).

The object inspection apparatus of the present invention scans terahertz waves on the specimen 1 at predetermined intervals to obtain an image of the specimen based on amplitude and phase signals collected from the specimen. And it may be implemented, for this purpose further comprises a transfer stage 60 for moving the specimen 1 planarly so that the terahertz wave output from the transmitter 10 can be scanned at a set interval (= step distance), In this case, the analyzer 50 may include imaging means for generating an image of the specimen 1 from the amplitude signal and the phase signal collected through the lock-in amplifier 40.

1 is a schematic diagram showing the configuration of a compact CW Terahertz Imaging System (Compact Continuous Wave Sub-Terahertz Imaging System) according to the present invention. Referring to FIG. 1, a conveyance for transporting the specimen 1 in the XZ direction A stage 60 is provided, and the specimen mounted on the transfer stage 60 to scan the terahertz wave of a predetermined frequency to the specimen 1 and receive the terahertz wave transmitted through the specimen ( It can be seen that the transmitter 10 is located at one side and the receiver 20 is located at the opposite side with respect to 1).

In addition, the reference signal generator 30 is connected to each oscillator output side of the transmitter and the receiver so as to receive the electromagnetic waves generated by the oscillator of the transmitter 10 and the receiver 20, wherein the reference signal generator 30 is It is also connected to the lock-in amplifier 40 to generate a reference signal from the electromagnetic waves input from the transmitter and the receiver and input the reference signal.

In addition, the lock-in amplifier 40 is connected to the receiver 20 to receive the measurement signal, and the lock-in amplifier 40 is connected to both the receiver 20 and the reference signal generator 30 to detect amplitude and phase of the measurement signal. As a result, the measurement signal and the reference signal are simultaneously received.

In the case of FIG. 1, a detector (indicated by 'Detector' in FIG. 5), in which the receiver 20 and the reference signal generator 30 are integrally formed, is connected to the transmitter 10 and the reference signal generator 30. The illustration is omitted for.

The lock-in amplifier 40 is a component for detecting the amplitude and phase of the measurement signal. The lock-in amplifier 40 processes the measurement signal input from the receiver 20 and the reference signal input from the reference signal generator 30 so as to be unique to the specimen. The amplitude signal and the phase signal output from the lock-in amplifier 40 are input to the imaging means 50 to be used to generate an image of the specimen 1.

At this time, the lock-in amplifier 40 detects and outputs the amplitude of the measurement signal input from the receiver 20, and amplifies the amplitude signal to separate and output the amplitude signal from other noise in the signal.

In addition, the reference signal input from the reference signal generator 30 is used as a phase detection standard signal to detect and output the phase of the measurement signal input from the receiver 20.

As an analysis device, the imaging means 50 converts an amplitude signal and a phase signal input from the lock-in amplifier 40 through the data collection unit 51 into an image (amplitude image and phase image) for the specimen 1. It may be a computer equipped with a program.

The amplitude signal and the phase signal input from the lock-in amplifier 40 are used alone in the imaging means 50, respectively, and are converted into the image of the specimen 1 (the amplitude image and the phase image, respectively), or the amplitude signal and the phase signal. Can be used at the same time to be converted into the image of the specimen ('amplitude + phase', 'amplitude-phase', 'phase-amplitude' image).

Meanwhile, the configuration of the transmitter, the receiver, and the reference signal generator in the present invention will be described in more detail with reference to FIGS. 2 to 4 as follows.

First, as shown in FIG. 2, the transmitter 10 is driven by a power box 11 that receives AC power and supplies power for driving and a power supplied by the power box 11 to a predetermined frequency. An oscillator 12 for generating and outputting electromagnetic waves, a power amplifier 13 driven by electric power supplied from the power box 11 to amplify and output electromagnetic waves input from the oscillator 12, and the power It comprises a frequency multiplier 14 for amplifying the electromagnetic wave output from the amplifier 13 by a predetermined multiple and outputting it as terahertz electromagnetic waves of a predetermined frequency.

Here, the oscillator 12 is a phase locked oscillator that generates and outputs electromagnetic waves having a fixed frequency, and a diode oscillator using a phase locked dielectric resonator (DRO) may be used.

The electromagnetic wave generated by the oscillator 12 is divided into two directions and outputted, one of which is input to a reference signal generator (reference numeral 30 in FIG. 5) and used to generate a reference signal, and the other is incident to the specimen. It is used to generate terahertz waves.

In order to generate terahertz waves, the electromagnetic waves generated by the oscillator 12 are input to the power amplifier 13 and amplified, and the electromagnetic waves amplified by the power amplifier 13 are measured in terahertz frequency in the frequency multiplier 14. Is amplified and output.

The frequency multiplier 14 may use a plurality of multipliers, which are passive elements, to amplify the electromagnetic waves amplified by the power amplifier 13 into terahertz waves, which are high frequencies.

As an embodiment of the transmitter 10, the oscillator 12 is configured to generate electromagnetic waves of 14.007 GHz by the power supplied from the power box 11, wherein the generated 14.007 GHz is a reference signal generator ( 30) and the power amplifier 13, the power amplifier 13 may be configured to amplify three times the electromagnetic wave of the oscillator 12 to output at 42.021 GHz.

After that, the frequency multiplier 14 amplifies the electromagnetic wave of 42.021 GHz output from the power amplifier 13 by three multipliers (x2 each), which are passive elements, by 8 times (x8), and the final 336.168 GHz (≒ 0.34 THz) electromagnetic wave. Will be output.

Next, as shown in FIG. 3, the receiver 20 is driven by a power box 21 that receives AC power and supplies power for driving, and electric power supplied from the power box 21. An oscillator 22 for generating and outputting electromagnetic waves of a predetermined frequency, a power amplifier 23 driven by electric power supplied from the power box 21 to amplify and output electromagnetic waves input from the oscillator 22, The frequency multiplier 24 amplifies and outputs the electromagnetic wave output from the power amplifier 23 by a predetermined multiple, and the terahertz wave received through the test object is mixed with the electromagnetic wave output from the frequency multiplier 24 to obtain IF ( A sub-harmonic mixer 25 for converting into an intermediate frequency signal, an IF amplifier 26 for amplifying and outputting an IF signal output from the sub-harmonic mixer 25, and the IF amplification; Filtering the amplified signal outputted from the 26 is configured to include a band-pass filter 27 to output the measurement signal of the predetermined frequency band.

Here, the oscillator 22 is a phase locked oscillator that generates and outputs electromagnetic waves of a frequency having a phase fixed as in a transmitter, and a diode oscillator using a phase locked dielectric resonator DRO may be used.

In addition, as in the transmitter, the electromagnetic wave generated in the oscillator 22 is divided into two directions and output, one of which is input to the reference signal generator 30 is used to generate a reference signal, the other from the transmitter 10 It is used to convert the terahertz wave signal received through the specimen to an IF signal.

The electromagnetic wave input from the oscillator 22 to the power amplifier 23 is amplified and input to the frequency multiplier 24. The frequency multiplier 24 of the receiver 20 is also a plurality of passive elements for amplification at high frequencies. Multipliers can be used.

As an embodiment of the receiver 20, the oscillator 22 is configured to generate electromagnetic waves of 14.000 GHz by the power supplied from the power box 21, wherein the generated 14.000 GHz is a reference signal generator ( 30) and the power amplifier 23, the power amplifier 23 may be configured to amplify twice the electromagnetic wave of the oscillator to output at 28.000 GHz.

Thereafter, the frequency multiplier 24 amplifies the electromagnetic wave of 28.000 GHz output from the power amplifier 23 by 6 times (x6) by two multipliers x2 and x3, which are passive elements, and outputs 168 GHz electromagnetic waves.

In the sub harmonic mixer 25 using this electromagnetic wave as a local oscillation signal, the IF signal down to the frequency of 168 MHz is output as shown below.

F) F _out = f _1-2 f ₂ = 336.168 GHz-2 x local oscillation signal from the transmitter (Tx) 168 GHz = 168 MHz

When the sub harmonic mixer 25 converts the received terahertz RF signal into an IF signal and outputs the same, the IF amplifier 26 amplifies and outputs a weak IF signal and is set by the band pass filter 27. Since only the frequency band is passed through and output, the final measurement signal can be output from the receiver 20.

Next, the present invention is characterized by having a reference signal generator 30 linked to the transmitter 10 and the receiver 20, as shown in Figure 4, the reference signal generator 30 and the transmitter A mixer 31 for receiving a phase-fixed electromagnetic wave output from each oscillator of the receiver and converting the electromagnetic wave into a frequency difference signal between the two electromagnetic waves and an amplifier for amplifying and outputting the frequency difference signal output from the mixer 31; 32), a frequency multiplier 33 for amplifying and outputting the frequency output from the amplifier 32 by a predetermined multiple, and amplified signal output from the frequency multiplier 33 to filter only the set frequency band to pass the reference signal. And a band pass filter 34 for final output.

In one embodiment of the reference signal generator 30 described above, a signal of 14.007 GHz input from an oscillator of a transmitter and a signal of 14.000 GHz input from an oscillator of a receiver are set by a mixer 31 at 7 MHz, which is a frequency difference between the two signals. An amplifier 32, a frequency multiplier 33, and a band pass filter 34 are configured to convert a 7 MHz frequency signal output from the mixer 31 into a final 168 MHz reference signal and output the converted frequency signal. Can be.

On the other hand, looking at the configuration of the entire system having the transmitter, the receiver, and the reference signal generator of the above configuration, as shown in Figure 5, the transmitter 10 is incident a terahertz wave to the specimen (1) mounted on the transport stage In this case, the receiver 20 detects the terahertz wave passing through the object and outputs it to the lock-in amplifier 40.

In addition, the reference signal generator 30 linked to the transmitter 10 and the receiver 20 generates a reference signal from the electromagnetic waves inputted from the transmitter and the receiver and outputs the reference signal to the lock-in amplifier 40. Thus, the lock-in amplifier 40 is The measurement signal of the receiver 20 and the reference signal of the reference signal generator 30 are read to finally output an amplitude signal and a phase signal representing information specific to the object.

As described above, the imaging means generates and outputs an image of the object under test based on the amplitude signal and the phase signal information divided and output from the lock-in amplifier.

Hereinafter, the present invention will be described in more detail based on the following examples, which are not intended to limit the present invention.

[Example]

In the above-described apparatus of the present invention, the terahertz wave is scanned at a predetermined interval (= step distance) to the sample 1 conveyed by the transfer stage 60 using the transmitter 10, and the receiver 20 is used. The amplitude and phase information were measured by detecting terahertz waves passing through the samples.

In this case, the configuration of the transmitter 10, the receiver 20, and the reference signal generator 30 used is the same as that of the embodiment described with reference to FIGS. 2 to 4.

That is, in the case of the transmitter 10, the oscillator 12 generates electromagnetic waves of 14.007 GHz, and the generated 14.007 GHz is input to the reference signal generator 30, and at the same time, the power amplifier 23 and the frequency multiplier 24 Finally, 336.168 GHz (≒ 0.34 THz) electromagnetic waves having a wavelength of about 0.9 mm were output.

In the case of the receiver 20, the oscillator 22 generates 14.000 GHz electromagnetic waves, and the generated 14.000 GHz is input to the reference signal generator 30, and is then passed through the power amplifier 23 and the frequency multiplier 24 to 168. GHz electromagnetic waves were configured to be input to the sub harmonic mixer 25.

At this time, in order to stably measure the high frequency of 0.34 THz, the sub harmonic mixer 25 was used to modulate an IF signal of 168 MHz to measure the signal.

In the reference signal generator 30, a 14.007 GHz signal input from the transmitter 10 and a 14.000 GHz signal input from the receiver 20 are converted into a frequency signal of 7 MHz, which is a frequency difference between the two signals by the mixer 31. The amplifier 32, the frequency multiplier 33, and the band pass filter 34 are configured to convert the 7 MHz frequency signal output from the mixer 31 into a final 168 MHz reference signal and output the converted signal.

On the other hand, variables such as the time delay (time to pause the device at the point of the sample for device stabilization) and the step distance of the scanning stage, which affect the resolution of the image during data acquisition, are used to obtain the imaging result. Two different samples were injected with terahertz waves and the results were measured and compared.

The image was measured by adjusting the time delay and the step distance affecting the spatial resolution, ie the aluminum slit, floppy disk, credit card as the sample to be tested.

At this time, the sample 1 was fixed and transported to the XZ transfer stage 60, and a terahertz wave was scanned in a point-by-point manner to obtain the image.

First, the image according to the step distance was measured using the aluminum slit as shown in FIG. 6 as a sample.

Samples of aluminum slit varying in the width of the slit from 0.5 to 3 mm with the gap between the slits kept constant at 5 mm were produced, and 0.34 THz (≒ 336.168) with the step distances of 1 mm and 0.1 mm, respectively. GHz) The images obtained by transmitting electromagnetic waves are shown in FIGS. 7A to 7D.

In the case of (a) and (b) measured with a step distance of 1 mm, the image measurement results of the amplitude and phase of the entire sample were shown.The steps (c) and (d) measured with a step distance of 0.1 mm showed only a part of the slit. The result was measured.

As can be seen from the measurement results, it was confirmed that the slit can be identified for both the amplitude and phase images of the step distance 1 mm and 0.1 mm, and the difference in resolution according to the step distance was also confirmed. The spread phenomenon at the edges of each slit is due to the diffraction of terahertz (THz) waves.

Also, when 0.34 THz electromagnetic waves were transmitted to floppy disks and credit cards, the transmittances of terahertz waves can be clearly distinguished according to the difference in the absorption rates of each part of the sample, and the difference in the step distance and time delay of the scanning stage in data collection. Has a significant effect on the resolution of the image.

8 (a) to 8 (d) and 9 (a) to (d) show terahertz (THz) imaging of floppy disks and credit cards at different time delays during data collection. Divided by

As shown in (a) and (b) of FIG. 8, when the time delay is 0.3 seconds, the shape of the sample can be identified, but the image resolution is inferior, whereas the image when the time delay is 1.5 seconds is shown in FIG. 8 (c). As shown in (d), much clearer images were obtained than in 0.3 seconds.

Similarly, in the case of a credit card, when the time delay is measured at 1.5 seconds, as shown in FIGS. 9 (c) and 9 (d), the time delay is measured at 0 seconds, compared to the image of FIGS. The image resolution of the chip, the rim, and the metal type inherent in the card showed excellent resolution.

Thus, in the present invention, by measuring the amplitude signal and the phase signal at the same time and imaging from the results it is possible to perform a more accurate measurement for a variety of samples in real-time continuous wave (CW) terahertz imaging.

On the other hand, the transmitter was used as a frequency source, but the image was measured using a pyroelectric detector (or sensor) 70 as a detector instead of the configuration of the receiver and the reference signal generator.

The pyroelectric detector 70 detects terahertz waves passing through the sample (1) to be tested and outputs only the amplitude signal representing the unique information of the sample. Therefore, when the pyroelectric detector is used, only the amplitude signal is used for imaging. To get a sample image.

The pyroelectric detector 70 as a terahertz (THz) detector has a high response in the sub-THz region and exhibits optimal output characteristics using a mechanical chopper 71 for the experiment. The modulation frequency of Hz was applied.

(A) and (b) of FIG. 10 measure the image of the aluminum slit when the step distances are different by the pyroelectric detector.

As with the result of using the transmitter-receiver (Tx-Rx) combination, a much sharper image was obtained at the step distance of 0.1 mm compared to the step distance of 1 mm.

In addition, (a) to (d) of FIG. 11 show the terahertz image measurement results of the floppy disk and the credit card, (a) and (c) shows the image of the sample at 0.3 seconds, and (b) and (d) Represent images of samples at 1.5 and 3 seconds, respectively.

As can be seen in the figure, the result of measuring the sample with the pyroelectric detector also achieved a much sharper image resolution when sufficient time delay was taken in collecting data as in the case of using the receiver (Rx).

Terahertz image measurements using a Tx-pyroelectric sensor show the same results as measurements of the transmitter-receiver system in terms of differences in image resolution for variables such as time delay and step distance. When comparing the images of the receiver and the pyroelectric detector, the image measurement using the transmitter-receiver combination shows better image resolution than the transmitter-pyroelectric detector combination.

12 (a) to 12 (d) are graphs showing the transmittances of aluminum slits measured by different detectors, and FIGS. 12 (a) and 12 (b) show steps 1 for each aluminum slit in the transmitter-receiver combination. mm and 0.1 mm, and (c) and (d) are graphs of transmittance in the transmitter-superelectric detector combination.

As can be seen, the terahertz (THz) transmittance graph measured by the transmitter-receiver combination shows a higher transmittance than the transmitter-pyroelectric detector, and a very stable alignment of terahertz waves through various width slits Indicates.

It can be seen that the difference between the transmittance and the graph alignment has a significant effect on the resolution of the image.

In conclusion, we measured various sample images using the time delay and the step distance of the scanning stage related to the image resolution, and the resolution of the image was much increased with the longer time delay and the shorter step distance. Could know.

In addition, the terahertz receiver using Schottky diode as a detector showed much clearer image results than the pyroelectric detector, and both the terahertz receiver and the pyroelectric detector showed very effective results in object identification.

13A to 13D illustrate images of a specimen obtained by using an object inspection apparatus (that is, a terahertz imaging device) according to the present invention, which are terahertz measurement images obtained by using leaves as the specimen to be inspected. .

FIG. 13A is an image obtained from an amplitude signal and a phase signal obtained using a terahertz receiver (THz Rx), respectively. FIGS. 13B, 13C, and 13D are images obtained by using both an amplitude signal and a phase signal. It is obtained using the method of obtaining the sum (Fig. 13B) or the subtract (Fig. 13C, 13D).

The phase signal can be used to obtain an image that contains new information not included in the amplitude image, and in some cases, it is possible to distinguish what is difficult to distinguish from the amplitude image.

The embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited to the above-described embodiments, and various modifications of those skilled in the art using the basic concepts of the present invention defined in the following claims and Improved forms are also included in the scope of the present invention.

1 is a schematic diagram showing the overall configuration of an object inspection apparatus according to the present invention composed of a terahertz imaging device.

2 is a block diagram showing the configuration of a transmitter in the object inspection apparatus according to the present invention.

3 is a block diagram showing the configuration of a receiver in the object inspection apparatus according to the present invention.

Figure 4 is a block diagram showing the configuration of a reference signal generator in the object inspection apparatus according to the present invention.

Figure 5 is a block diagram schematically showing the overall configuration of the object inspection apparatus according to the present invention.

6 is a view showing an aluminum slit sample used when measuring the image of the object inspection apparatus according to the present invention.

FIG. 7 shows image measurement results of the aluminum slit shown in FIG. 6, (a) an amplitude image at a step distance of 1 mm, (b) a phase image, (c) an amplitude image at a step distance of 0.1 mm, and FIG. (b) shows a phase image.

Figure 8 shows the results of the image measurement of the floppy disk using the object inspection apparatus according to the present invention, (a) amplitude image, (b) phase image, and time delay of 1.5 seconds time delay (c) Amplitude image and (b) phase image.

Figure 9 shows the result of measuring the image of the credit card using the object inspection apparatus according to the present invention, (c) amplitude image, (b) phase image, and time delay of 1.5 seconds time delay (c) Amplitude image and (b) phase image.

FIG. 10 shows the results of measuring the image of the aluminum slit shown in FIG. 6 using a pyroelectric detector, (a) an image at a step distance of 1 mm and (b) an image at a step distance of 0.1 mm. will be.

Figure 11 shows the measurement results of the floppy disk and credit card using a superelectric detector, (a) floppy disk image, (c) credit card image, and time delay of 1.5 seconds at 0.3 seconds delay (b) A) a floppy disk image, (d) a credit card image.

Figure 12 shows the results of measuring the transmittance of the aluminum slit, (a) step distance 1 mm, (b) step distance 0.1 mm measured by the transmitter-receiver combination according to the present invention, and transmitter-pyroelectric detector combination The transmittance graphs of (c) step distance 1 mm and (d) step distance 0.1 mm were measured.

13A to 13D illustrate various images of a specimen obtained using an object inspection apparatus (ie, a terahertz imaging apparatus) according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1: Sample (sample) 10: Transmitter

20: receiver 30: reference signal generator

40: lock-in amplifier 50: analyzer (imaging means)

Claims (9)

A transmitter 10 generating a terahertz wave and incident on the specimen 1; A receiver 20 which receives the terahertz wave incident from the transmitter 10 and passes through the object 1 and outputs it as a measurement signal modulated with an IF signal; A reference signal generator 30 for converting a signal input from the transmitter 10 and the receiver 20 to generate a reference signal; A lock-in amplifier 40 receiving the measurement signal of the receiver 20 and the reference signal of the reference signal generator 30 and outputting an amplitude signal and a phase signal detected from the measurement signal; An analyzer (50) for analyzing inherent information of the specimen using at least one of an amplitude signal and a phase signal collected from the lock-in amplifier (40); Object inspection apparatus using a terahertz wave comprising a. The method according to claim 1, It further comprises a transfer stage 60 for moving the specimen 1 planarly so that the terahertz wave output from the transmitter 10 can be scanned at intervals set in the specimen, The analyzer 50 uses at least one of an amplitude signal and a phase signal collected from the lock-in amplifier 40 during the terahertz wave scan on the specimen 1 moved by the transfer stage 60. An apparatus for inspecting an object using terahertz waves, comprising: imaging means for converting the image into an image for an object to be inspected. The method according to claim 1, The transmitter 10, A power box 11 receiving power and supplying driving power; An oscillator 12 which receives the driving power and generates and outputs electromagnetic waves; A power amplifier (13) for receiving the driving power and amplifying the electromagnetic waves input from the oscillator (12); A frequency multiplier (14) for amplifying the electromagnetic wave input from the power amplifier (13) by a predetermined multiple and outputting it as terahertz waves incident on the specimen (1); Object inspection apparatus using a terahertz wave, characterized in that it comprises a. The method according to claim 1, The receiver 20, A power box 21 receiving power and supplying driving power; An oscillator 22 which receives the driving power and generates and outputs electromagnetic waves; A power amplifier 23 which receives the driving power and amplifies the electromagnetic waves input from the oscillator 22; A frequency multiplier 24 for amplifying the electromagnetic wave input from the power amplifier 23 by a predetermined multiple; A sub harmonic mixer (25) for mixing the terahertz waves received through the specimen (1) with the electromagnetic waves output from the frequency multiplier (24) to convert them into IF signals; An IF amplifier 26 for amplifying the IF signal input from the sub harmonic mixer 25; A band pass filter 27 for filtering the amplified signal input from the IF amplifier 26 and outputting the measured signal as a measured signal of a set frequency band; Object inspection apparatus using a terahertz wave, characterized in that it comprises a. The method according to claim 3 or 4, The oscillator (12, 22) is an object inspection apparatus using a terahertz wave, characterized in that the phase-locked oscillator for generating and outputting a fixed phase electromagnetic wave. The method according to claim 5, The phase locked oscillator is a terahertz wave object inspection apparatus, characterized in that the diode oscillator using a dielectric resonator. The method according to claim 3 or 4, The reference signal generator 30 is connected to the output side of the oscillators 12 and 22, and the electromagnetic wave signals output from the oscillators 12 and 22 are input to the reference signal generator 30 and used to generate the reference signals. An object inspection apparatus using a terahertz wave, characterized in that. The method according to claim 1, The reference signal generator 30, A mixer (31) for receiving the electromagnetic wave signals input from the transmitter (10) and the receiver (20) and converting them into frequency difference signals between the two electromagnetic waves; An amplifier (32) for amplifying and outputting a frequency difference signal input from the mixer (31); A frequency multiplier (33) for amplifying the amplified signal input from the amplifier (32) by a predetermined multiple; A band pass filter 34 for filtering the amplified signal input from the frequency multiplier 33 and outputting the amplified signal as a reference signal of a set frequency band; Object inspection apparatus using a terahertz wave, characterized in that it comprises a. The method according to claim 1, The lock-in amplifier 40 detects the phase of the measurement signal and outputs a phase signal using a reference signal input from the reference signal generator 30 as a phase detection standard signal. Inspection device. .

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