KR20160149429A

KR20160149429A - High-speed 3D imaging system using THz beam scan

Info

Publication number: KR20160149429A
Application number: KR1020150086363A
Authority: KR
Inventors: 이대수; 양지상
Original assignee: 한국표준과학연구원
Priority date: 2015-06-18
Filing date: 2015-06-18
Publication date: 2016-12-28
Also published as: KR101702380B1

Abstract

The present invention relates to a high-speed three-dimensional image detecting apparatus using a THz beam scan, and an object of the present invention is to provide a high-speed three-dimensional image detecting apparatus using a THz beam scan, which is capable of obtaining a three- Speed three-dimensional image detection apparatus.

Description

[0001] The present invention relates to a high-speed 3D imaging system using THz beam scanning,

The present invention relates to a high-speed three-dimensional image detecting apparatus using THz beam scanning, more particularly, to a three-dimensional image detecting apparatus capable of obtaining a three-dimensional image at a high speed by non-destructive and non- Speed three-dimensional image detection apparatus using THz beam scanning.

Measurement of the shape of objects is very important and indispensable in the technical fields of the industry as a whole, and various research and development are actively performed. For example, in the case of a two-dimensional image measurement technique for measuring a fine shape on a two-dimensional plane, for example, a line width of a semiconductor integrated circuit or a pattern defect, foreign matter, asymmetry, etc., an imaging device such as an optical microscope and a CCD camera And a technique for acquiring such a two-dimensional image has been already widely used in a general optical microscope or an electron microscope field and is widely used.

As the necessity of acquiring information about the three-dimensional shape increases in the two-dimensional image, the technique of measuring the three-dimensional shape or the inner shape of the object surface as well as the shape of the outer surface of the object is also variously Development has been done. For example, it is a technique such as imaging and detecting a three-dimensional structure inside a living body, discriminating an object contained in a container, detecting a crack in an object, and the like. The basic premise of this object measurement is that it should be able to measure non-destructive method, and it is better if it can be measured by non-contact method.

One of the simplest non-destructive and non-contact detection techniques is to acquire projection images, and X-ray technology can be an example. As is well known, when an object is irradiated with an X-ray, which is a transparent electromagnetic wave, and X-rays transmitted through the object are detected, the amount of X-rays detected depending on the amount of X- A two-dimensional projection image of the three-dimensional object can be obtained.

Terahertz (THz) beams are also highly transmissive electromagnetic waves that can transmit a variety of nonconductive materials such as fibers and plastics. Unlike X-rays, the photon energy is not high enough to damage living tissue or DNA, There is an advantage of high biological safety compared to Korean Patent Laid-Open No. 2005-0024303 ("Terahertz Imaging System and Method ", Mar. 3, 2005, hereinafter referred to as Prior Art 1) has been disclosed as an image acquisition technique using a THz beam. The prior art document 1 is a technique of obtaining a two-dimensional image as a principle similar to an X-ray, and more specifically, it is as follows. Similar to X-rays, the THz beam also transmits a specific transmission or reflection spectrum during the transmission of the object. Accordingly, the THz beam is irradiated to the object, and then the THz beam transmitted through the object is measured, You can get the image. In the prior art document, in order to enable the detection of explosives or biological weapons concealed in containers, such as a person or a suitcase, a seal package, etc., to be effectively and quickly carried out in the prior art document 1, Discloses a technique for constructing a more accurate image by simultaneously detecting signals reflected or transmitted from the region of interest at a plurality of points. This non-destructive inspection technique using THz beam is utilized as a technique such as checking whether a weapon exists in a body of a traveler or an airplane in a travel bag at an airport search center.

On the other hand, the projection image obtained using the X-ray and THz beams as described above can provide only two-dimensional information on the three-dimensional object. Techniques such as computed tomography (CT), optical coherence tomography (OCT), and the like have been used as techniques for revealing a more accurate three-dimensional structure of an object. These techniques are commonly used in the medical field to image three-dimensional structures inside the living body. The CT technique is a technique of obtaining an X-ray projection image of an object in various angles and then reconstructing the images to generate a tomographic image or a three-dimensional image. In addition, OCT technology is a technology to image the microstructure inside the object by using optical interference phenomenon. It is a technology that is in the spotlight in the medical field in particular because it can acquire the microstructure inside the biotissue while minimizing the damage of the biotissue to be.

However, as is well known in the art, it takes a lot of time to shoot a CT image because several hundreds to several thousand two-dimensional projection images are obtained at different angles with respect to an object. That is, the time efficiency of application of the 3D shape detection technology using the CT imaging method to the other fields of the medical field is extremely bad. On the other hand, in the case of OCT technology, studies on light output, stability, and speed improvement are actively performed, but there is a limitation that the depth of the three-dimensional imaging is only a few millimeters, which can be limitedly applied to diagnosis of the retina or application to endoscopic techniques.

However, as described above, the technologies developed and used up to now have a limitation due to the specialization that has been studied according to the characteristics of each technology, and thus, It is difficult to apply them to various industrial fields. The technology to detect 3D images that can be applied to a wide variety of industrial fields needs to be able to detect a wide variety of objects by reducing restrictions on materials and sizes. What is most urgently needed is that high-speed and high-precision measurements should be possible.

In the case of the imaging technique using the THz beam, since the object can be transmitted, it is possible to acquire the three-dimensional image through the combination of other technologies at present and there is a fear that the object may be damaged when compared with the X- And it is possible to detect objects with a much greater depth when compared with OCT technology. That is, the THz beam has various characteristics suitable for use as a next generation high-speed three-dimensional imaging technique. However, many researches on imaging technology using THz beam are still in the beginning stage and there are many problems to be solved.

A method of obtaining a three-dimensional image using a THz beam is divided into a transmission type and a reflection type. The transmissive type is similar to the CT method described above. Since the THz beam is used instead of the X-ray, there is an advantage that the biological stability is high. However, the CT technique has the longest problem of long measurement time. The reflection type system uses a TOF (Time-Of-Flight) principle, that is, a method of acquiring information in the depth direction (that is, the beam traveling direction) by calculating the distance using the time that the beam is irradiated, to be. Since the THz beam also has a property of being transmissive but reflected at the interface, the position information of the interfaces existing in the depth direction of the object can be known by detecting the reflection signal and calculating the position where the reflection signal is generated, The three-dimensional shape information inside the object can be obtained as a result by irradiating the depth direction information with respect to a plurality of points on the two-dimensional plane perpendicular to the surface. FIG. 1 is a schematic view of a conventional three-dimensional imaging apparatus using a reflection type THz beam, in which a THz beam is irradiated to a sample to obtain a reflected signal, and the object is two-dimensionally moved have. More specifically, "High-speed terahertz reflection three-dimensional imaging for nondestructive evaluation" (Kyung Hwan Jin, Young-Gil Kim, Seung Hyun Cho, Jong Chul Ye, Dae-Su Yee, 25 November 2012 / No. 23 / OPTICS EXPRESS, hereinafter referred to as Prior Art 2).

Prior art 2 has made considerable technological leaps in the field of 3D image detection technology in that it can detect high-precision three-dimensional image using THz beam. However, since the object must be physically moved on a two-dimensional plane, there is a limit in speed and precision even in the prior art document 2, and it is required to improve the speed.

1. Korean Patent Publication No. 2005-0024303 ("Terahertz Imaging System and Method ", Mar. 10, 2005)

1. "High-speed terahertz reflection three-dimensional imaging for nondestructive evaluation" (Kyung Hwan Jin, Young-Gil Kim, Seung Hyun Cho, Jong Chul Ye, Dae-Su Yee, 25 November 2012 / Vol. / OPTICS EXPRESS) 2. "High-speed terahertz time-domain spectroscopy based on electronically controlled optical sampling" (Youngchan Kim and Dae-Su Yee, OPTICS LETTERS / Vol. 35, No. 22 / November 15, 2010)

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a THz beam, which can acquire a three- Speed three-dimensional image detecting apparatus using scan.

According to an aspect of the present invention, there is provided an apparatus for detecting a high-speed three-dimensional image using a THz beam scan, the apparatus comprising: a THz beam detecting unit for irradiating a THz beam onto an object to detect a reflected signal reflected; A galvanometer scanner for adjusting the THz beam direction angle and a telecentric f-θ lens for irradiating the angle-controlled THz beam toward the object, wherein the THz beam is incident on the object A two-dimensional scanning unit for adjusting a two-dimensional position to be irradiated; And a controller for calculating the depth information of the object shape using a time-of-flight (TOF) method using the reflection signal detected by the THz-beam detecting unit, Dimensional position information on which the depth information is generated, and to calculate the three-dimensional shape information of the object.

More specifically, the present invention relates to a high-speed three-dimensional image detecting apparatus using a THz beam scanning method, in which a first laser having a pulse repetition rate and a time delay between pulses generated at the same pulse repetition rate, A variable delay time generation unit 110 including a first laser 111 and a second laser 112 and periodically varying the time delay between the first laser 111 and the second laser 112, ; A cross correlator 121 for generating a cross-correlation signal at a moment when a time delay becomes 0 between optical pulses output from the first laser 111 and the second laser 112 using a cross correlation, And a digital pulse generator 122 for generating a digital pulse. The digital pulse generator 122 generates a pulse based on the cross-correlation signal generated by the cross-correlator 121, A trigger signal generator 120 for outputting a trigger signal; A detector 132 for detecting a THz beam by the second laser 112, a detector 132 for detecting the progress of the THz beam emitted from the oscillator 131, A beam splitter 133 disposed on the optical path for allowing the THz beam emitted from the oscillator 131 to pass therethrough and reflecting the THz beam reflected from the object 500 to be incident on the detector 132, And a digitizer 134 for digitizing the THz beam reflection signal detected by the detector 132 and the angle adjustment driving signal of the two-dimensional scan driver 150 based on the trigger signal generated by the signal generator 120 A THz beam detecting unit 130; A galvanometer scanner 141 that receives a THz beam emitted from the oscillator 131 and adjusts a direction of a THz beam, a THz beam whose angle is adjusted by the galvanometer scanner 141, A THz beam scanner 140 comprising a telecentric f-? A two-dimensional scan driver 150 for controlling the angle adjustment of the galvanometer scanner 141 based on a trigger signal generated by the digital pulse generator 122; The digitizer 134 receives the digitized THz beam reflection signal and the digitized angle adjustment driving signal and analyzes the THz beam reflection signal to calculate the depth information of the object 500 shape, A data processing unit 160 for calculating two-dimensional position information on the object 500 on which the THz beam reflected signal is generated and analyzing the three-dimensional shape information of the object 500; . &Lt; / RTI >

The two-dimensional scan driver 150 includes a waveform signal generator 151 for generating a driving waveform signal based on a trigger signal generated by the digital pulse generator 122, a waveform signal generator 151 And at least one rotation driving unit 152a and 152b for rotating the galvanometer scanner 141 using the driving waveform signal transmitted from the driving waveform signal.

The THz beam detecting unit 130 is provided on a signal transmission path between the detector 132 and the digitizer 134 and amplifies the signal detected by the detector 132 and transmits the amplified signal to the digitizer 134 An amplifier 135 may be provided.

The THz beam detector 130 may also focus the THz beam that is used for collimation of the THz beam from the oscillator 131 or reflected by the beam splitter 133 to the detector 132 axis parabolic mirror 136, which is used to focus the light beam onto the substrate.

Also, the oscillator 131, the detector 132, the beam splitter 133, the off-axis parabolic mirrors 136, the galvanometer scanner 141, the telecentric the f-theta lens 142 is composed of a head unitized as an integral unit and an oscillator and a detector combined with an optical fiber as the oscillator 131 and the detector 132 are used, ). At this time, it is preferable that an optical fiber femtosecond laser is used as the first laser and the second laser of the time delay variable laser generation unit 110 so that the time delay variable laser generation unit 110 and the head are connected to each other by an optical fiber Do.

According to the present invention, a three-dimensional image of an object is acquired using a THz beam, thereby solving the problems inherent in existing 3D image acquisition technologies. Compared to X-ray technology, which is likely to cause damage to living tissue, there is less risk of damage to the object and the stability is significantly improved. The range of depth detection is less than that of OCT technology, There is an advantage to be improved dramatically.

Above all, according to the present invention, there is a great effect of enabling detection at a much higher speed than in the prior art. More specifically, the present invention obtains depth direction information using a THz beam but in a reflective manner, which is advantageous when compared to a conventional CT technique or similar, THz beam transmission type three- There is no need to acquire the transmission image at the time of the measurement. Therefore, there is a great effect that the measurement time can be saved dramatically. Also, in the reflection type system using the conventional THz beam, when the object is two-dimensionally moved during the three-dimensional image acquisition, the depth direction information is obtained for a plurality of points on the two- Method has limitations in improving the speed and precision in the process of physically moving the object. However, according to the present invention, the beam irradiation position on the two-dimensional plane can be changed by changing the irradiation direction of the THz beam while fixing the object. As a result, the beam irradiation position changing speed is remarkably improved compared with the conventional art, and the problem of the precision lowering due to the physical movement of the object has been solved in the past, and ultimately, the THz beam There is a great effect that the three-dimensional shape detection that is used can be realized.

Also, in the conventional method, it was impossible to detect the shape of the fixed (i.e., non-movable) object because the measurement was performed while moving the object physically. On the other hand, the THz beam scanning method of the present invention can not detect It also has the effect of enabling shape detection.

1 is a schematic view of a conventional imaging apparatus using a THz beam;
2 is a schematic diagram of a high-speed three-dimensional image detection apparatus using the THz beam scan of the present invention.
3 shows a THz beam scanner.
FIG. 4 shows an embodiment of a high-speed three-dimensional image detecting apparatus using THz beam scanning according to the present invention.
5 is an illustration of a three-dimensional image of an actual object detected by the apparatus of the present invention.

Hereinafter, a high-speed 3D image detecting apparatus using THz beam scanning according to the present invention having the above-described structure will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic diagram of a high-speed three-dimensional image detecting apparatus using THz beam scanning according to the present invention. A high-speed three-dimensional image detecting apparatus using THz beam scanning according to the present invention includes a THz beam detecting unit and a two-dimensional scanning unit, as schematically shown in FIG.

The THz beam detector detects a reflected signal by irradiating a THz beam onto an object, and the 2D scanner controls a two-dimensional position where the THz beam is irradiated onto the object. That is, the apparatus of the present invention may further include a step of calculating the depth information of the object shape using a time-of-flight (TOF) method using the reflection signal detected by the THz beam detecting unit, Dimensional position information in which the depth information is generated, and ultimately, the three-dimensional shape information of the object is calculated.

Detection of depth information using THz beam reflection is made by the following principle. First, when the object is irradiated with the THz beam, if the refractive index of the material forming the object is uniform, the THz beam propagates through the object, but is reflected at the portion where the refractive index changes, that is, at the interface. At this time, the depth information of the interface where the THz beam is reflected can be calculated by measuring the time delay of the reflected signal from which the THz beam is reflected.

At this time, in the present invention, the two-dimensional scanning unit includes a galvanometer scanner for adjusting a direction of a THz beam and a telecentric f-θ lens for irradiating a THz beam whose angle is adjusted by the galvanometer scanner toward an object . The telecentric f-theta lens is a lens that allows an incident light beam to have a constant direction and a focal length irrespective of the angle, and Fig. 3 shows the principle of the telecentric f-theta lens. In other words, when rays having different angles are incident on the telecentric f-theta lens, the rays passing through the telecentric f-theta lens focus on the same focal distance, and these foci form the focal plane. Here, the two-dimensional position of the focus on the focal plane is equal to the product of the angle of the ray and the focal length of the telecentric f-theta lens.

In the case of the imaging apparatus using the conventional THz beam shown in FIG. 1, the object itself is physically moved in the two-dimensional direction by using a translation stage. As a result, There has been a problem in that a problem occurs. However, according to the present invention, since the galvanometer scanner adjusts the direction of the THz beam direction by adjusting the two-dimensional position of the THz beam irradiated on the object, it is not necessary to directly move the object. As is well known, a galvanometer scanner is a device configured to rotate a small mirror according to an applied voltage. Since the mirror to be moved is small and lightweight, generation of moment is small and high-speed and high-precision driving is easy. That is, since the moving stage equipped with the detection object is relatively large and heavy, driving of the galvanometer scanner can be performed at a much higher speed and with high precision compared to physically moving the detection target.

As described above, the angle of the THz beam can be known through the rotation drive signal value of the galvanometer scanner. By the angle of the ray incident on the telecentric f-theta lens as described above, Dimensional position is determined. That is, when an object is positioned on the focal plane of the telecentric f-theta lens, the two-dimensional position of the THz beam on the object can be easily known using the rotation drive signal value of the galvanometer scanner.

How to calculate the three-dimensional shape information of the object with the apparatus of the present invention constructed as described above will be described in more detail as follows. If the medium constituting the object is uniform, the THz beam will be reflected from the top surface (surface) of the object and the bottom surface (bottom) of the object. When a THz beam is irradiated to a position (x1, y1) on a certain two-dimensional image on the object, the reflected signal reflected from the object's top surface has a time delay of? T11 and the reflected signal reflected at the object's bottom is? (I.e., depth information) z12 corresponding to the distance values (i.e., depth information) z11 and t12 corresponding to? T11 can be calculated. That is, from the result that the reflection signal having two time delay values (? T11,? T12 in this example) was measured, the object at the (x1, y1) point has the uppermost surface at the z11 position in the depth direction and the lowest surface at the z12 position You can see the information that you have.

In other cases, when a THz beam is irradiated to another point (x2, y2) on a two-dimensional plane, it is assumed that the reflected signals having four different time delay values are measured. In this case, The depth information values are denoted as z21, z22, z23, and z24. This means that the material traveling through the THz beam at the (x2, y2) position is changed four times, that is, there are four interfaces. Specifically, z21 is the top surface depth information of the object, z24 is the bottom surface depth information of the object, and z22 and z23 are coordinates of some other material (e.g., crack) existing in the object at the (x2, y2) Depth information of the uppermost and lowermost interfaces.

As described above, the object depth information (z11, z12, etc.) at a certain two-dimensional position can be calculated using the THz beam detecting unit, and the two-dimensional position value (x1, y1), etc.). The three-dimensional shape of the object can be completely reconstructed by acquiring the depth information values (z11, z12, etc.) of the interfaces existing at points on a plurality of two-dimensional points (x1, y1, etc.) and integrating them.

Fig. 2 schematically shows only a part of the main part of the apparatus of the present invention, and a more specific embodiment is shown in Fig. 4 is a more detailed embodiment of a high-speed three-dimensional image detecting apparatus using THz beam scanning according to the present invention. 4, the high-speed three-dimensional image detecting apparatus using THz beam scanning according to the present invention includes a time delay variable laser generating unit 110, a trigger signal generating unit 120, a THz beam detecting unit 130, a THz A two-dimensional scan unit including a beam scanner 140 and a two-dimensional scan driver 150, and a data processor 160. Hereinafter, each part will be described in more detail.

The time delay variable laser generation unit 110 includes a first laser 111 and a second laser 112 that have the same pulse repetition rate and have a time delay between generated pulses, ). At this time, the time delay variable laser generation unit 110 is formed such that a time delay between the first laser 111 and the second laser 112 is periodically variable. As will be described in more detail below, the first laser 111 is used for oscillating the THz beam, the second laser 112 is used for detecting the THz beam, and the first laser 111 and the second laser The depth information of the object can be easily and quickly detected through the time delay variation of the object.

The trigger signal generator 120 includes the cross-correlator 121 and the digital pulse generator 122. The trigger signal generator 120 generates the trigger signal based on the cross-correlation signal generated by the cross- The pulse generating unit 122 generates a pulse and outputs a trigger signal. The following explains each part.

The cross-correlator 121 generates a cross correlation signal at a moment when the time delay becomes zero between the optical pulses output from the first laser 111 and the second laser 112. As shown in the figure, the cross-correlator 121 includes a lens for receiving the first laser 111 and the second laser 112, a nonlinear crystal (NC) provided at a focus position of the lens, And a photodetector (PD, Photo Detector) for detecting an optical signal generated from the nonlinear crystal.

The digital pulse generator 122 generates digital pulses, and operates in conjunction with the correlator 121, thereby outputting a trigger signal. As described above, one of the optical pulses of the two lasers generated in the time delay variable laser generator 110 has a time delay value, and the time delay value is periodically varied with time. The cross-correlator 121 generates a cross-correlation signal at a moment when the time delay between the optical pulses of the two lasers becomes zero, and the digital pulse generator 122 generates a trigger signal accordingly, Take the time reference for the operation of each part and the calculation of information.

The THz beam detector 130 includes an oscillator 131, a detector 132, a beam splitter 133, and a digitizer 134 as shown. The THz beam detector 130 includes an amplifier 135, off-axis parabolic mirrors 136 may be additionally provided.

The oscillator 131 emits a THz beam by the first laser 111 and the detector 132 detects the THz beam by the second laser 112. There are various methods such as a photoconductive method and an optical rectification method for generating a THz beam, and there are also various methods such as a photoconductive method and an electro-optic sampling method for detecting a THz beam . Generally, one femtosecond pulse laser is divided into a beam splitter, one of which is used for THz oscillation and the other is used for THz detection, and a time delay device is provided on one of the two optical paths. The THz waveform can be measured by detecting the intensity of the electric field of the THz beam by optical sampling while varying the time delay. However, since the conventional time delay device is configured to change the time delay by the movement of the position, the change of the time delay is slow and the measurement of the THz waveform is slow.

In the present invention, unlike the conventional method, a time delay is periodically varied between the first laser 111 used for oscillation and the second laser 112 used for detection, , The THz beam oscillation and detection is the same as the conventional method, but the THz waveform can be measured much more quickly. As described above, in the time delay variable laser generation unit 110, the time delay value is periodically varied with time. For example, the time delay value between the two lasers at time t1 is? T1, The time delay between the two lasers at? And so on. More detailed operation principles of the time delay variable laser generation unit 110 are described in "High-speed terahertz time-domain spectroscopy based on electronically controlled optical sampling" (Youngchan Kim and Dae-Su Yee, OPTICS LETTERS / Vol. 22 / November 15, 2010), and the description thereof is omitted here.

The beam splitter 133 is disposed on the traveling path of the THz beam emitted from the oscillator 131 and transmits the THz beam emitted from the oscillator 131 and transmits the THz beam reflected from the object 500 Reflects the beam, and makes the beam incident on the detector 132. As shown in FIG. 4, the THz beam emitted from the oscillator 131 is irradiated to the object 500 through the THz beam scanner 140 to be described later, and the beam reflected from the object 500 is incident on the beam 500, The optical path is changed such that the light is incident on the detector 132 by the splitter 133. [

The digitizer 134 receives the THz beam reflection signal detected by the detector 132 and the angle adjustment driving signal of the two-dimensional scan driver 150 based on the trigger signal generated by the trigger signal generator 120 It plays a role of digitizing. Here, the THz beam reflection signal means a detection signal generated in the detector 132 by the reflected THz beam, not the reflected THz beam itself.

In order to allow the THz beam reflected signal detected by the detector 132 to be recognized more smoothly in the process of being transmitted to the digitizer 134, An amplifier 135 is further provided to amplify a signal detected by the detector 132, that is, a THz beam reflected signal, and transmit the amplified signal to the digitizer 134. [

In addition, the THz beam detector 130 may further include at least one off-axis parabolic mirror 136 as shown. The off-axis parabolic mirror 136 is basically used for collimation and focusing of the THz beam. More specifically, the non-condensing parabolic mirror 136 is provided on the THz beam path from the oscillator 131 to cause the THz beam to be collimated or the THz beam path to be reflected by the beam splitter 133 The non-condensing parabolic mirror 136 may be provided to focus the THz beam onto the detector 132.

The THz beam scanner 140 includes a galvanometer scanner 141 and a telecentric f-θ lens 142 as shown. In addition, the two-dimensional scan driver 150 controls the angle adjustment of the galvanometer scanner 141. For reference, the combination of the THz beam scanner 140 and the two-dimensional scan driver 150 to be described below corresponds to the two-dimensional scan unit in the schematic configuration of FIG.

The galvanometer scanner 141 receives a THz beam emitted from the oscillator 131 and adjusts a direction of a THz beam. The telecentric f-θ lens 142 is disposed on the galvanometer scanner 141, The angle of which is controlled by the THz beam. In this case, the functions of the corresponding devices in the simplified structure of FIG. 2 are the same as those of the corresponding devices.

The two-dimensional scan driver 150 controls the angle adjustment of the galvanometer scanner 141 based on the trigger signal generated by the digital pulse generator 122, as described above. As described above with reference to the simplified structure of FIG. 2, the angle of the galvanometer scanner 141 is adjusted to change the two-dimensional irradiation position of the THz beam. As will be described later in detail, A certain amount of time is required. That is, the THz beam stays at a certain position on the two-dimensional surface for a predetermined time, and the THz beam moves to another position on the two-dimensional surface and remains at the position. At this time, the time point at which the THz beam is fixed to the two-dimensional position or moved to another position is determined based on the trigger signal generated in the trigger signal generator 120.

The configuration of the two-dimensional scan driver 150 will be described in more detail as follows. The two-dimensional scan driver 150 includes a waveform signal generator 151 for generating a driving waveform signal based on a trigger signal generated by the digital pulse generator 122, And at least one rotation driving unit 152a and 152b that rotates the galvanometer scanner 141 using the driving waveform signal transmitted from the galvanometer scanner 151. For the two-dimensional scanning, the two-dimensional scan driver 150 drives the two mirrors provided in the galvanometer scanner 141 to rotate. That is, the THz beam is sequentially reflected on the two mirrors of the galvanometer scanner 141 and is incident on the telecentric f-theta lens 142. The two-dimensional position is determined by the angles of the two mirrors, At this time, the two rotation driving units 152a and 152b in the two-dimensional scan driving unit 150 rotate the two mirrors in the galvanometer scatter 141, respectively. More specifically, the two-dimensional scan driver 150 can perform a raster scan by driving one of the two mirrors of the galvanometer scanner 141 to rotate rapidly and the other to rotate slowly have.

The data processing unit 160 receives the digitized THz beam reflection signal and the digitized angle adjustment driving signal from the digitizer 134 and analyzes the THz beam reflected signal to calculate depth information of the shape of the object 500 Dimensional position information on the object 500 on which the THz beam reflection signal is generated by analyzing the angle adjustment driving signal and calculating the three-dimensional shape information of the object 500. [ As described above, the trigger signal is generated in the trigger signal generator 120 at the moment when the time delay between the optical pulses of the two lasers becomes zero in the time delay variable laser generator 110, The THz beam detecting unit 130 and the two-dimensional scan unit operate on the basis of the time delay of the time-delayed variable laser generation unit 110. As a result, do.

The apparatus for detecting high-speed three-dimensional images using the THz beam scanning according to the present invention having the above-described structure is characterized in that, based on the trigger signal using the time delay variable laser generation unit 110, Dimensional scanning (C-scan) can be performed, and the THz beam detecting unit can perform A-scan in a fast depth direction, ultimately realizing high-speed three-dimensional scanning.

4, the oscillator 131, the detector 132, the beam splitter 133, the off-axis parabolic mirrors 136, the galvanometer scanner 141, The telecentric f-theta lens 142 is displayed in a form of a rectangle indicated by [HEAD]. This means that the components listed above can be configured as a unitized unit head. That is, when the actual devices are constituted, the above-described components are constituted by one head, thereby making it possible to make the device compact and practical.

In addition, the oscillator 131 and the detector 132 may be configured to be portable by using an optical fiber coupled oscillator and a detector. In this case, if an optical fiber femtosecond laser is used as the first laser and the second laser of the time delay variable laser generation unit 110, the head that is movably formed with the time delay variable laser generation unit 110 is easily connected to the optical fiber .

Figure 5 shows a three-dimensional image of an actual object detected by the apparatus of the present invention. FIG. 5A is a schematic view of a sample of glass fiber reinforced polymer (GFRP) used as a target. In FIG. 5A, the blue portion is a PTFE (Polytetrafluoroethylene) And the red and green colored portions indicate the peeled portions. That is, a sample having a different material or a peeling layer internally formed according to the design of FIG. 5 (a) was manufactured and it was tested whether an accurate three-dimensional image could be obtained with the apparatus shown in FIG. More specifically, the GFRP samples were 100 mm, 100 mm, and 3 mm in width, 100 mm, and 3 mm, respectively, and PTFE having a thickness of 0.025 mm at a blue display position and a 1.5 mm depth position were present, And a release layer having a thickness of 0.2 mm was formed at a depth of 1 mm and 2 mm. Also, while the pulse repetition rate of the first laser 111 and the second laser 112 is synchronized at 100 MHz in the time delay variable laser generation unit 110, the time delay is periodically variable from 1 kHz to about 60 ps Respectively. At this time, 725 pieces of depth direction information (A-scan data) can be obtained repeatedly at a speed of 1 kHz. That is, the depth direction information of 1,000 positions on the two-dimensional plane can be obtained in one second. On a two-dimensional scale, 200 horizontal and 200 horizontal positions were measured, and the time taken for this measurement was 40 seconds. In addition, it takes 10 seconds to measure 100 positions in 100 dimensions on two dimensions. The telecentric f-theta lens used in the experiment of Fig. 5 is also an axisymmetric lens.

5 (b) is a two-dimensional (C-scan) image obtained as a result of the experiment, and FIG. 5 (c) is a reconstructed three-dimensional image using depth direction information. As shown in the figure, a three-dimensional detection image can be obtained which confirms that foreign matter exists at a position corresponding to previously known sample information. In particular, as described above, the measurement time for obtaining the three- It did not catch. That is, it was confirmed that the high-speed three-dimensional image detection using the THz beam scanning can be realized through the apparatus of the present invention as shown in FIG. 5 and the like.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It goes without saying that various modifications can be made.

110: Time delay variable laser generator
111: first laser 112: second laser
120: Trigger signal generator
121: cross correlator 122: digital pulse generator
130: THz beam detection unit
131: Oscillator 132: Detector
133: beam splitter 134: digitizer
135: amplifier 136: parabolic mirror
140: THz Beam Scanner
141: galvanometer scanner 142: telecentric f-theta lens
150: a two-dimensional scan driver
151: a waveform signal generating unit 152a, b:
160:
500: object

Claims

A THz beam detecting unit for irradiating a THz beam on an object to detect a reflected signal reflected;
A galvanometer scanner for adjusting the THz beam direction angle and a telecentric f-θ lens for irradiating the angle-controlled THz beam toward the object, wherein the THz beam is incident on the object A two-dimensional scanning unit for adjusting a two-dimensional position to be irradiated;
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The depth information of the object shape is calculated using a TOF (Time-Of-Flight) method using the reflection signal detected by the THz beam detecting unit, and the depth information is generated using the angle adjusting driving signal of the two- Dimensional position information,
And the three-dimensional shape information of the object is calculated.

And a first laser 111 and a second laser 112 having the same pulse repetition rate and having a time delay between generated pulses, wherein the first laser 111 111) and the second laser (112) so that the time delay between the laser and the second laser (112) changes periodically;
A cross correlator 121 for generating a cross-correlation signal at a moment when a time delay becomes 0 between optical pulses output from the first laser 111 and the second laser 112 using a cross correlation, And a digital pulse generator 122 for generating a digital pulse. The digital pulse generator 122 generates a pulse based on the cross-correlation signal generated by the cross-correlator 121, A trigger signal generator 120 for outputting a trigger signal;
A detector 132 for detecting a THz beam by the second laser 112, a detector 132 for detecting the progress of the THz beam emitted from the oscillator 131, A beam splitter 133 disposed on the optical path for allowing the THz beam emitted from the oscillator 131 to pass therethrough and reflecting the THz beam reflected from the object 500 to be incident on the detector 132, And a digitizer 134 for digitizing the THz beam reflection signal detected by the detector 132 and the angle adjustment driving signal of the two-dimensional scan driver 150 based on the trigger signal generated by the signal generator 120 A THz beam detecting unit 130;
A galvanometer scanner 141 that receives a THz beam emitted from the oscillator 131 and adjusts a direction of a THz beam, a THz beam whose angle is adjusted by the galvanometer scanner 141, A THz beam scanner 140 comprising a telecentric f-?
A two-dimensional scan driver 150 for controlling the angle adjustment of the galvanometer scanner 141 based on a trigger signal generated by the digital pulse generator 122;
The digitizer 134 receives the digitized THz beam reflection signal and the digitized angle adjustment driving signal and analyzes the THz beam reflection signal to calculate the depth information of the object 500 shape, A data processing unit 160 for calculating two-dimensional position information on the object 500 on which the THz beam reflected signal is generated and analyzing the three-dimensional shape information of the object 500;
And a high-speed three-dimensional image detecting device using THz beam scanning.

The apparatus of claim 2, wherein the two-dimensional scan driver (150)
A waveform signal generator 151 for generating a driving waveform signal based on the trigger signal generated by the digital pulse generator 122,
And at least one rotation driving part (152a) (152b) for rotating the galvanometer scanner (141) using the driving waveform signal received from the waveform signal generating part (151) High Speed 3D Image Detection System Using Scan.

The apparatus as claimed in claim 2, wherein the THz beam detecting unit (130)
And an amplifier 135 provided on the signal transmission path between the detector 132 and the digitizer 134 for amplifying the signal detected by the detector 132 and transmitting the amplified signal to the digitizer 134 High Speed 3D Image Detection Using THz Beam Scanning.

The apparatus as claimed in claim 2, wherein the THz beam detecting unit (130)
At least one non-condensing mirror used to collimate the THz beam from the oscillator 131 or to focus the THz beam reflected at the beam splitter 133 onto the detector 132, and an off-axis parabolic mirror (136).

6. The method of claim 5,
The oscillator 131, the detector 132, the beam splitter 133, the off-axis parabolic mirrors 136, the galvanometer scanner 141, the telecentric f- the? lens 142 is constituted by a head integrally unitized,
Wherein the head is movable by using an optical fiber coupled oscillator and a detector as the oscillator 131 and the detector 132. The high speed three dimensional image detecting apparatus of claim 1,

The method according to claim 6,
Wherein the time delay variable laser generation unit 110 and the head are connected by an optical fiber by using an optical fiber femtosecond laser as the first laser and the second laser of the time delay variable laser generation unit 110, High Speed 3D Image Detection System Using Scan.