Denoising apparatus and method for terahertz imaging system

Abstract

A denoising apparatus and method for a terahertz imaging system are disclosed, and a denoising method for a terahertz imaging system according to one embodiment of the present invention may include the steps of applying a terahertz signal to an object to acquire raw data, extracting envelope data of the raw data, and visualizing signal-processed data for a voltage response output extracted from the envelope data.

Description

Technology Field

[0001] The present invention relates to a denoising apparatus and method for a terahertz imaging system. For example, the present invention relates to a noise reduction technique for improving image quality of a sub-terahertz transmission imaging system. Background Technology

[0002] Terahertz waves exhibit frequency characteristics for polar and non-polar materials, and have high resolution due to their shorter wavelengths compared to conventional electromagnetic waves.

[0003] In this regard, Figure 1 is a conceptual diagram illustrating the characteristics of terahertz waves.

[0004] Referring to Fig. 1, terahertz waves are being widely studied in various application fields recently due to their advantage of being harmless to the human body. In particular, terahertz waves have the characteristic of being able to obtain high-resolution transmission images, so they can be utilized in various imaging systems such as non-destructive inspection, detection of foreign substances in food, and airport security checkpoints.

[0005] Such a terahertz imaging system consists of a transmitter that generates, amplifies, and radiates terahertz signals, a receiver that detects objects based on scattering, reflection, and absorption characteristics, and a signal processing unit that processes the detected signals.

[0006] Meanwhile, one of the indicators representing the characteristics of an imaging system using a terahertz detector is the signal-to-noise ratio (SNR).

[0007] The signal-to-noise ratio (SNR) of an imaging system plays a crucial role in obtaining sharp and clear terahertz images. In the case of plasmon detectors using low-cost CMOS processes, there is a problem in that the SNR is degraded by DC offset or 1 / f noise because the detector output is output in the form of a DC voltage.

[0008] Although these problems can be improved by using a mechanical chopper and adjusting the modulation frequency, there are limitations in that not only is the image SNR and output stability degraded due to vibrations of the mechanical chopper, but flux may also occur in the acquired data due to external noise.

[0009] The technology forming the background of this invention is disclosed in Korean Registered Patent Publication No. 10-2111369. The problem to be solved

[0010] The present invention aims to solve the problems of the aforementioned prior art and to provide a denoising apparatus and method for a terahertz imaging system capable of achieving improved image signal-to-noise ratio characteristics.

[0011] However, the technical problems that the embodiments of the present invention aim to solve are not limited to the technical problems described above, and other technical problems may exist. means of solving the problem

[0012] As a technical means for achieving the above-mentioned technical problem, a denoising method for a terahertz imaging system according to one embodiment of the present invention may include the steps of: applying a terahertz signal to an object to acquire raw data; extracting envelope data of the raw data; and visualizing signal-processed data for a voltage response output extracted from the envelope data.

[0013] In addition, the step of extracting the envelope data can extract the upper envelope data and the lower envelope data of the raw data separately.

[0014] In addition, the imaging step can image the signal-processed data using a voltage response based on the difference information between the average information of the upper envelope data and the average information of the lower envelope data.

[0015] In addition, the step of extracting the envelope data may include the step of deriving the upper envelope data and the lower envelope data, respectively, using a Hilbert filter and a Kaiser window.

[0016] Additionally, the step of extracting the envelope data may include a step of deriving first difference information, which is difference information obtained when the terahertz signal passes through the object and is applied to the detector, and a step of deriving second difference information, which is noise difference information obtained from the detector itself when the terahertz signal is reflected by the object and is not applied to the detector.

[0017] In addition, the step of extracting the envelope data may include the step of calculating the voltage response based on the presence or absence of the object using the first difference information and the second difference information.

[0018] In addition, a denoising method for a terahertz imaging system according to one embodiment of the present invention may include, after the step of acquiring raw data, a step of removing a DC offset component using the average of the raw data.

[0019] Meanwhile, a denoising device for a terahertz imaging system according to one embodiment of the present invention may include a collection unit that acquires raw data by applying a terahertz signal to an object, an envelope analysis unit that extracts envelope data of the raw data, and an imaging processing unit that visualizes signal-processed data regarding a voltage response output extracted from the envelope data.

[0020] In addition, the envelope analysis unit can separate and extract the upper envelope data and the lower envelope data of the raw data.

[0021] In addition, the imaging processing unit can image the signal-processed data using a voltage response based on the difference information between the average information of the upper envelope data and the average information of the lower envelope data.

[0022] In addition, the envelope analysis unit can derive the upper envelope data and the lower envelope data, respectively, using a Hilbert filter and a Kaiser window.

[0023] In addition, the envelope analysis unit can derive first difference information, which is difference information obtained when the terahertz signal passes through the object and is applied to the detector, and second difference information, which is noise difference information obtained from the detector itself when the terahertz signal is reflected by the object and is not applied to the detector.

[0024] In addition, the envelope analysis unit can calculate the voltage response based on the presence or absence of the object using the first difference information and the second difference information.

[0025] In addition, a denoising device for a terahertz imaging system according to one embodiment of the present invention may include an offset removal unit that removes a DC offset component using the average of the raw data.

[0026] Meanwhile, a terahertz imaging system according to one embodiment of the present invention may include a transmitting module that generates and amplifies a terahertz signal and radiates the terahertz signal toward an object, a receiving module having a detector that acquires raw data generated when the terahertz signal is incident on the object, and a signal processing module having a denoising device that extracts envelope data of the raw data and visualizes the raw data based on the envelope data.

[0027] The means for solving the problem described above are merely exemplary and should not be interpreted as intended to limit the present invention. In addition to the exemplary embodiments described above, additional embodiments may exist in the drawings and the detailed description of the invention. Effects of the invention

[0028] According to the means for solving the problem of the present invention described above, a denoising apparatus and method for a terahertz imaging system capable of achieving improved image signal-to-noise ratio characteristics can be provided.

[0029] However, the effects obtainable from this invention are not limited to those described above, and other effects may exist. Brief explanation of the drawing

[0030] Figure 1 is a conceptual diagram illustrating the characteristics of terahertz waves. FIG. 2 is a schematic diagram of a terahertz imaging system according to one embodiment of the present invention. Figure 3 is a diagram illustrating an exemplary detector layout and an object to be measured. Figure 4 is a conceptual diagram illustrating the output characteristics of a detector according to the presence or absence of metal masking. Figure 5 is a conceptual diagram illustrating the output characteristics using the modulation frequency of a plasmon detector. Figure 6 is a diagram showing a comparison between the ideal output waveform and the actual output waveform due to noise when acquiring data through a mechanical chopper or power on-off operation. Figure 7 is a conceptual diagram illustrating the problem of inaccurate voltage response measurement when applying conventional terahertz signal processing techniques. Figures 8a and 8b are graphs showing data obtained by distinguishing between the presence or absence of the object. FIG. 9 is a conceptual diagram illustrating a voltage response calculation method based on envelope data according to a denoising device for a terahertz imaging system according to one embodiment of the present invention. FIG. 10 is a diagram showing a comparison of the quality of image data obtained by a terahertz imaging system according to one embodiment of the present invention and image data obtained when a conventional signal processing technique is applied. FIG. 11 is a schematic diagram of a denoising device for a terahertz imaging system according to one embodiment of the present invention. FIG. 12 is an operation flowchart for a denoising method for a terahertz imaging system according to one embodiment of the present invention. Specific details for implementing the invention

[0031] Embodiments of the present invention are described below with reference to the attached drawings to enable those skilled in the art to easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0032] Throughout this specification, when a part is described as being "connected" to another part, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" or "indirectly connected" with other elements interposed between them.

[0033] Throughout the entire specification, when a component is described as being located "on," "on top," "on top," "under," "on bottom," or "on bottom" of another component, this includes not only cases where the component is in contact with the other component but also cases where another component exists between the two components.

[0034] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0035] The present invention relates to a denoising apparatus and method for a terahertz imaging system. For example, the present invention relates to a noise reduction technique for improving image quality of a sub-terahertz transmission imaging system.

[0036] FIG. 2 is a schematic diagram of a terahertz imaging system according to one embodiment of the present invention.

[0037] Referring to FIG. 2, a terahertz imaging system (10) according to one embodiment of the present invention may include a transmitting module (11), a receiving module (21), and a signal processing module (31). Specifically, the transmitting module (11) may include a signal generator (101) and a modulator (102), and the receiving module (21) may include a power supply (201) and a detector (202). Additionally, the signal processing module (31) may include a denoising device (100) for a terahertz imaging system according to one embodiment of the present invention (hereinafter referred to as 'denoising device (100)'), a data collector (301), and a user terminal (302).

[0038] Meanwhile, the transmitting module (11), receiving module (21), and signal processing module (31) of the terahertz imaging system (10) disclosed herein may communicate with each other through a network (not shown). The network (not shown) refers to a connection structure capable of exchanging information between each node, such as terminals and servers. Examples of such a network (not shown) include, but are not limited to, a 3GPP (3rd Generation Partnership Project) network, an LTE (Long Term Evolution) network, a 5G network, a WIMAX (World Interoperability for Microwave Access) network, the Internet, a LAN (Local Area Network), a Wireless LAN (Wireless Local Area Network), a WAN (Wide Area Network), a PAN (Personal Area Network), a Wi-Fi network, a Bluetooth network, a satellite broadcasting network, an analog broadcasting network, and a DMB (Digital Multimedia Broadcasting) network.

[0039] The user terminal (302) may be any type of wireless communication device, such as a smartphone, smartpad, tablet PC, etc., and a PCS (Personal Communication System), GSM (Global System for Mobile communication), PDC (Personal Digital Cellular), PHS (Personal Handyphone System), PDA (Personal Digital Assistant), IMT (International Mobile Telecommunication)-2000, CDMA (Code Division Multiple Access)-2000, W-CDMA (W-Code Division Multiple Access), or Wibro (Wireless Broadband Internet) terminal. For example, the user terminal (302) may be a device for displaying an image of an object (1) that has been visualized using a terahertz signal by a denoising device (100).

[0040] Additionally, although FIG. 2 discloses that the denoising device (100) disclosed herein is provided as a separate and independent device from the detector (202), user terminal (302), etc., according to an embodiment of the present invention, the denoising device (100) may be a sub-module mounted on the detector (202) or user terminal (302).

[0041] FIG. 3 is a diagram illustrating an exemplary detector layout and an object to be measured. Specifically, FIG. 3(a) is a layout image of a single detector (202) included in a terahertz imaging system (10), and FIG. 3(b) is an exemplary illustration of an object (1) corresponding to a sample to be measured by the terahertz imaging system (10). For example, the sample shown in FIG. 3(b) is a sample made using a copper film having a thickness of 0.06 mm.

[0042] Referring to FIG. 3, the detector (202) according to one embodiment of the present invention may be a power detector. To facilitate a more specific understanding, the detector (202) may be a plasmon detector or a resistive mixed characteristic detector, but is not limited thereto. Meanwhile, when acquiring data in a terahertz imaging system (10) based on a plasmon detector, when a terahertz signal is incident on the detector (202), a DC voltage and a voltage due to noise are generated at the output, and when the signal is reflected by an object such as metal and does not enter the detector (202), only a voltage due to noise is generated, so data can be acquired based on the voltage difference depending on the presence or absence of the terahertz signal. In addition, the detector (202) can detect an object by reflecting electromagnetic wave characteristics such as reflection, diffraction, and scattering that occur when a terahertz signal is incident on an object (1).

[0043] More specifically, when a receiving module (21) is configured using a detector (202) of the CMOS plasmon detector type that utilizes the plasmon effect, the plasmon effect is utilized, which means that when the operating frequency of the transistor included in the detector (202) is lower than the frequency of the incident signal, a direct current (DC) voltage is generated at the drain node due to the voltage difference between the source node and the drain node, and accordingly, a direct current (DC) voltage appears at the drain output of the detector (202) in proportion to the strength of the terahertz signal applied to the target (1).

[0044] For example, in the description of the embodiments of the present invention, the detector (202) may be a unit detector composed of a folded dipole antenna operating in a predetermined frequency band (e.g., 0.2 THz, etc.) to acquire terahertz image data, a detector core, and a buffer amplifier, but is not limited thereto.

[0045] In this regard, the performance indicator of the detector (202) is voltage responsivity (R V It can be expressed in terms of ) and Noise Equivalent Power (NEP), among which voltage response (R V ) represents the ratio of the difference in output voltage of the detector (202) to the incident power as shown in Equation 1 below, and the noise equivalent power (NEP) may represent the point where the ratio of signal to noise becomes 1 in a 1 Hz bandwidth as shown in Equation 2 below. Meanwhile, even if detectors (202) have the same responsiveness, a detector (202) with lower noise equivalent power may be evaluated as having superior performance.

[0046] [Equation 1]

[0047]

[0048] [Equation 2]

[0049]

[0050] Figure 4 is a conceptual diagram illustrating the output characteristics of a detector according to the presence or absence of metal masking.

[0051] Referring to FIG. 4, depending on the characteristics of the terahertz signal, if metal masking is present, the terahertz signal is reflected by the metal masking portion, and only noise is generated at the output of the detector (202). In contrast, if there is no metal masking portion, the applied terahertz signal can pass through the target (1) and be incident on the detector (202), so that noise and a DC voltage for the incident terahertz signal are generated at the output of the detector (202).

[0052] In this regard, the signal-to-noise ratio (SNR) of image data generated by a terahertz signal can be calculated as the ratio of the maximum voltage to the minimum voltage among the output DC voltage values ​​obtained for a single frame, as shown in Equation 3 below.

[0053] [Equation 3]

[0054]

[0055] Figure 5 is a conceptual diagram illustrating the output characteristics of a plasmon detector.

[0056] Referring to FIG. 5, in the case of a plasmon detector, as shown in FIG. 5 (a), the output of the detector (202) is output in the form of a direct current (DC) voltage, so the SNR may be degraded by DC offset or 1 / f noise, and this problem can be improved by raising the DC voltage to the modulation frequency using a mechanical chopper or an electrical chopper as shown in FIG. 5 (b).

[0057] Figure 6 is a diagram showing a comparison between the ideal output waveform and the actual output waveform due to noise when acquiring data through a mechanical chopper or power on-off operation.

[0058] Referring to FIG. 6, when data is acquired using the method using the aforementioned mechanical chopper or through an electrical chopper, such as a power source on-off operation, f m Assuming is a modulated signal, f s When assuming that the terahertz signal is a sampled signal, if we assume an ideal case as shown in FIG. 6 (a), when the terahertz signal is on, a DC voltage appears as a clean sampling waveform at the output of the detector (202), and when it is off, nothing should be output at the output of the detector (202). However, in reality, as shown in FIG. 6 (b), the image quality is degraded because flux is generated due to noise caused by the vibration of the mechanical chopper or noise introduced from the outside.

[0059] Meanwhile, FIG. 7 is a conceptual diagram illustrating the problem of inaccurate voltage response measurement when applying conventional terahertz signal processing techniques. Specifically, FIG. 7 (a) is a conceptual diagram illustrating a method (Min-Max method) for calculating voltage response using the difference between the maximum and minimum values ​​obtained in the on-off state of the terahertz signal, and FIG. 7 (b) is a conceptual diagram illustrating a method (Peak method) for calculating voltage response using the difference between the average values ​​of the upper peak and lower peak of the data obtained in the on-off state of the terahertz signal.

[0060] Referring to Fig. 7, when the first method, the Min-Max method, among the aforementioned conventional signal processing methods is applied, the quality of the image resulting from the imaging may be degraded. In the case of the second method, the Peak method, data higher than the average value may be misidentified as a lower peak value, or data lower than the average value may be misidentified as an upper peak value, which may cause distortion in the data. Consequently, there is a limitation in that the voltage response cannot be accurately measured by the conventional signal processing method, and as a result, the signal-to-noise ratio characteristics of the image are degraded.

[0061] Below, the specific functions and operations of the denoising device (100) devised to solve the problems of the aforementioned conventional technology will be described in detail.

[0062] The denoising device (100) can acquire raw data by applying a terahertz signal to an object (1). For example, the denoising device (100) may apply modulation using a preset modulation frequency (e.g., 200 Hz, etc.) and acquire raw data based on a preset sampling frequency (e.g., 8 kHz, etc.), but is not limited thereto. In other words, according to one embodiment of the present invention, the terahertz signal is a modulation frequency (f m It can be applied in an On / Off form, and the denoising device (100) has a predetermined sampling frequency (f s Through ), data (raw data) such as that shown in blue in Figures 8a and 8b described later can be extracted.

[0063] In this regard, FIGS. 8a and 8b are graphs showing data obtained depending on the presence or absence of an object. Specifically, FIGS. 8a and 8b show data obtained depending on the presence or absence of an object, specifically when a terahertz signal passes through and enters the detector (202) when an object is present, and when a terahertz signal is reflected when no object is present.

[0064] Additionally, the denoising device (100) can calculate the average of the acquired raw data. Additionally, the denoising device (100) can remove the DC offset component included in the raw data using the calculated average of the raw data.

[0065] Additionally, the denoising device (100) can extract envelope data of raw data from which the DC offset component has been removed. Specifically, the denoising device (100) can extract the upper envelope data (High envelope) and lower envelope data (Low envelope) of the raw data separately.

[0066] For example, the graph portion drawn in blue in FIG. 8a represents raw data acquired in response to a state in which a terahertz signal is applied to the detector (202) by a part where the metal of the object (1) is not present, the graph portion drawn in red in FIG. 8a represents upper envelope data derived from raw data in the On state, and the graph portion drawn in yellow in FIG. 8a represents lower envelope data derived from raw data in the Off state.

[0067] Likewise, the graph portion drawn in blue in FIG. 8b represents raw data obtained in response to the state in which a terahertz signal is reflected by the metal part of the object (1), the graph portion drawn in red in FIG. 8b represents upper envelope data derived from the raw data in the On state, and the graph portion drawn in yellow in FIG. 8b represents lower envelope data derived from the raw data in the Off state.

[0068] In this regard, according to one embodiment of the present invention, a denoising device (100) can derive upper envelope data and lower envelope data, respectively, using a Hilbert filter and a Kaiser window. At this time, the Hilbert filter is applied to obtain only the data size from raw data from which the DC offset has been removed, and the Kaiser window can be applied to attenuate the side lobes of the data.

[0069] In addition, the denoising device (100) can calculate the average information (average value) of the upper envelope data and the average information (average value) of the lower envelope data, respectively.

[0070] For example, as illustrated in FIG. 8a, when a terahertz signal passes through an object (1), the average information (average value) of the upper envelope data can be calculated as 0.12V, and the average information (average value) of the lower envelope data can be calculated as 0.04V. In contrast, as illustrated in FIG. 8b, when a terahertz signal is reflected by an object (1), the average information (average value) of the upper envelope data can be calculated as 0.09V, and the average information (average value) of the lower envelope data can be calculated as 0.07V.

[0071] Additionally, the denoising device (100) can calculate difference information (difference between average values) between the average information of the upper envelope data and the average information of the lower envelope data.

[0072] FIG. 9 is a conceptual diagram illustrating a voltage response calculation method based on envelope data according to a denoising device for a terahertz imaging system according to one embodiment of the present invention.

[0073] Referring to FIG. 9(a), the denoising device (100) can derive a first difference information, which is the difference information between the average information of the upper envelope data and the average information of the lower envelope data obtained in response to the state in which a terahertz signal passes through the object (1) and is applied to the detector (202). For example, from the data shown in FIG. 8a, the first difference information between the average information of the envelope data can be calculated as 0.08V.

[0074] Additionally, referring to FIG. 9(b), the denoising device (100) can derive second difference information, which is the difference between the average information of the upper envelope data and the average information of the lower envelope data, obtained in response to a state where the terahertz signal is reflected by the object (1) and not applied to the detector (202). For example, from the data shown in FIG. 8b, the second difference information between the average information of the envelope data can be calculated as 0.02V.

[0075] Additionally, the first difference information and the second difference information obtained by the denoising device (100) may correspond to the reaction voltage (△V) of the detector (202), and using this, the voltage response (R) according to the presence or absence of the object (1) V ) can be produced.

[0076] Specifically, the denoising device (100) can visualize signal-processed data for a voltage response output extracted from envelope data from first difference information and second difference information based on the following Equation 4.

[0077] [Equation 4]

[0078]

[0079] Additionally, the denoising device (100) can image the raw data obtained based on the envelope data. Specifically, the denoising device (100) can calculate the voltage response using the difference information between the average information of the upper envelope data and the average information of the lower envelope data.

[0080] FIG. 10 is a diagram showing a comparison of the quality of image data obtained by a terahertz imaging system according to one embodiment of the present invention and image data obtained when a conventional signal processing technique is applied. Specifically, the left image of FIG. 10 (a) represents image data processed using the Min-Max method, the right image of FIG. 10 (a) represents image data processed using the Peak method, and FIG. 10 (b) represents image data derived by applying signal processing using envelope data by the denoising device (100) disclosed in the present invention.

[0081] Comparing FIG. 10 (a) and (b), it can be confirmed that high-quality image data is produced by the denoising device (100) disclosed herein, and the signal-to-noise ratio (SNR) characteristic is also found to be at the level of 22.4 dB, which is a significant improvement of approximately 3.8 dB and 9 dB, respectively, compared to existing methods. These experimental results show not only a high SNR value but also accurate voltage response (R V This means that measuring ) is important for improving image quality by removing noise from terahertz transmission images.

[0082] FIG. 11 is a schematic diagram of a denoising device for a terahertz imaging system according to one embodiment of the present invention.

[0083] Referring to FIG. 11, the denoising device (100) may include a data collection unit (110), an offset removal unit (120), an envelope analysis unit (130), and an image processing unit (140).

[0084] The data collection unit (110) can obtain raw data by applying a terahertz signal to the target (1).

[0085] The offset removal unit (120) can calculate the average of the acquired raw data. Additionally, the offset removal unit (120) can remove the DC offset component included in the raw data using the calculated average of the raw data.

[0086] The envelope analysis unit (130) can extract envelope data of raw data from which DC offset components have been removed. Specifically, the envelope analysis unit (130) can separate and extract the upper envelope data (High envelope) and lower envelope data (Low envelope) of the raw data.

[0087] In this regard, according to one embodiment of the present invention, the envelope analysis unit (130) can derive upper envelope data and lower envelope data, respectively, using a Hilbert filter and a Kaiser window.

[0088] In addition, the envelope analysis unit (130) can calculate the average information (average value) of the upper envelope data and the average information (average value) of the lower envelope data, respectively.

[0089] Additionally, the envelope analysis unit (130) can calculate the difference information (the difference between the average values) between the average information of the upper envelope data and the average information of the lower envelope data.

[0090] Additionally, according to one embodiment of the present invention, the envelope analysis unit (130) can derive a first difference information which is the difference information between the average information of the upper envelope data and the average information of the lower envelope data obtained in response to a state in which a terahertz signal passes through the object (1) and is applied to the detector (202), and can derive a second difference information which is the difference information between the average information of the upper envelope data and the average information of the lower envelope data obtained in response to a state in which a terahertz signal is reflected by the object (1) and is not applied to the detector (202).

[0091] Additionally, the envelope analysis unit (130) uses the first difference information and the second difference information obtained corresponding to the On state and Off state, respectively, to obtain the voltage response (R) associated with the detector (202). V ) can be produced.

[0092] The imaging processing unit (140) can image signal-processed data regarding voltage response outputs extracted from envelope data. Specifically, the imaging processing unit (140) can image signal-processed data by assuming the object (1) as a single frame (1 Frame) and using the voltage response obtained at each point (point) of the frame. At this time, the imaging processing unit (140) can obtain an image SNR by using the difference between the point (point) with the highest voltage response and the point (point) with the lowest voltage response within the frame.

[0093] In other words, the image processing unit (140) can operate to acquire an image of the object (1) using the voltage response at each point obtained by the envelope analysis unit (130) using the first difference information and the second difference information through data processing of the raw data.

[0094] Below, based on the details described above, we will briefly examine the operation flow of the present invention.

[0095] FIG. 12 is an operation flowchart for a denoising method for a terahertz imaging system according to one embodiment of the present invention.

[0096] The denoising method for a terahertz imaging system illustrated in FIG. 12 can be performed by the denoising device (100) described above. Therefore, even if the details are omitted below, the description of the denoising device (100) can be applied in the same way to the description of the denoising method for a terahertz imaging system.

[0097] Referring to FIG. 12, in step S11, the data collection unit (110) can obtain raw data by applying a terahertz signal to the target (1).

[0098] Additionally, in step S11, the offset removal unit (120) can calculate the average of the acquired raw data.

[0099] Next, in step S12, the offset removal unit (120) can remove the DC offset component included in the raw data using the average of the calculated raw data.

[0100] Next, in step S13, the envelope analysis unit (130) can extract envelope data of the raw data from which the DC offset component has been removed.

[0101] Specifically, in step S13, the envelope analysis unit (130) can distinguish and extract the upper envelope data (High envelope) and lower envelope data (Low envelope) of the raw data.

[0102] In addition, according to one embodiment of the present invention, in step S13, the envelope analysis unit (130) can derive upper envelope data and lower envelope data, respectively, using a Hilbert filter and a Kaiser window.

[0103] Next, in step S141, the envelope analysis unit (130) can calculate the average information (average value) of the upper envelope data.

[0104] Additionally, in step S142, the envelope analysis unit (130) can calculate the average information (average value) of the lower envelope data.

[0105] Next, in step S15, the envelope analysis unit (130) can calculate the difference information (the difference between the average values) between the average information of the upper envelope data and the average information of the lower envelope data.

[0106] Next, in step S16, the imaging processing unit (140) can image the signal-processed data for the voltage response output extracted from the envelope data.

[0107] Specifically, in step S16, the imaging processing unit (140) can image the signal-processed data using the voltage response based on the difference information between the average information of the upper envelope data derived through step S15 and the average information of the lower envelope data.

[0108] In the description above, steps S11 through S16 may be further divided into additional steps or combined into fewer steps according to an embodiment of the present invention. Additionally, some steps may be omitted as necessary, and the order of the steps may be changed.

[0109] A denoising method for a terahertz imaging system according to one embodiment of the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the medium may be those specifically designed and configured for the present invention, or may be those known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs and DVDs; magneto-optical media such as floptical disks; and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include machine code, such as that generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The above-described hardware device may be configured to operate as one or more software modules to perform the operation of the present invention, and vice versa.

[0110] In addition, the denoising method for the aforementioned terahertz imaging system can also be implemented in the form of a computer program or application executed by a computer that is stored on a recording medium.

[0111] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical concept or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0112] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and the concept of equivalents thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0113] 10: Terahertz Imaging System 11: Transmission module 101: Signal Generator 102: Modulator 21: Receiver Module 201: Power supply 202: Detector 31: Signal processing module 100: Denoising device for terahertz imaging systems 110: Data Collection Unit 120: Offset removal section 130: Envelope Analysis Section 140: Image processing unit 301: Data Acquisition (DAQ) 302: User terminal

Claims

Claim 1 A denoising method for a terahertz imaging system comprises: a step of acquiring raw data by applying a terahertz signal to an object; a step of extracting envelope data of the raw data; and a step of imaging signal-processed data for a voltage response output extracted from the envelope data, wherein the step of extracting envelope data comprises distinguishing and extracting upper envelope data and lower envelope data of the raw data, and the step of extracting envelope data comprises deriving each of the upper envelope data and the lower envelope data using a Hilbert filter and a Kaiser window. Claim 2 delete Claim 3 A denoising method according to claim 1, wherein the imaging step involves imaging the signal-processed data using a voltage response based on the difference information between the average information of the upper envelope data and the average information of the lower envelope data. Claim 4 delete Claim 5 A denoising method according to claim 3, wherein the step of extracting envelope data comprises: a step of deriving first difference information, which is difference information obtained by the terahertz signal passing through the object and being applied to the detector; and a step of deriving second difference information, which is noise difference information obtained by the detector itself, which is noise difference information obtained by the terahertz signal being reflected by the object and not applied to the detector. Claim 6 A denoising method according to claim 5, wherein the step of extracting envelope data further includes the step of calculating the voltage response based on the presence or absence of the object using the first difference information and the second difference information. Claim 7 A denoising method according to claim 1, further comprising the step of removing a DC offset component using the average of the raw data after the step of acquiring the raw data. Claim 8 A denoising device for a terahertz imaging system comprises: a collection unit that acquires raw data by applying a terahertz signal to an object; an envelope analysis unit that extracts envelope data of the raw data; and an imaging processing unit that visualizes signal-processed data for a voltage response output extracted from the envelope data, wherein the envelope analysis unit separates and extracts upper envelope data and lower envelope data of the raw data, and the envelope analysis unit derives the upper envelope data and the lower envelope data, respectively, using a Hilbert filter and a Kaiser window. Claim 9 delete Claim 10 In claim 8, the denoising device wherein the imaging processing unit images the signal-processed data using a voltage response based on the difference information between the average information of the upper envelope data and the average information of the lower envelope data. Claim 11 delete Claim 12 A denoising device according to claim 10, wherein the envelope analysis unit derives first difference information, which is difference information obtained when the terahertz signal passes through the object and is applied to the detector, and derives second difference information, which is noise difference information obtained from the detector itself when the terahertz signal is reflected by the object and is not applied to the detector. Claim 13 In claim 12, the envelope analysis unit calculates the voltage response based on the presence or absence of the object using the first difference information and the second difference information, in a denoising device. Claim 14 A denoising device according to claim 8, further comprising an offset removal unit that removes a DC offset component using the average of the raw data. Claim 15 An imaging system comprising: a transmitting module that generates and amplifies a terahertz signal and radiates the terahertz signal toward an object; a receiving module having a detector that acquires raw data generated when the terahertz signal is incident on the object; and a signal processing module having a denoising device that extracts envelope data of the raw data and visualizes the raw data based on the envelope data, wherein the signal processing module separates and extracts upper envelope data and lower envelope data of the raw data, and the signal processing module derives the upper envelope data and the lower envelope data, respectively, using a Hilbert filter and a Kaiser window.

Images