JP2018010012A - Measurement object information acquisition device and method for the acquisition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement object information acquisition device which can easily and correctly observe information on a measurement object.SOLUTION: The measurement object information acquisition is for acquiring a time waveform by a time-domain spectroscopy and acquiring information on a measurement object, and includes: a terahertz wave generation unit 101; a detection unit 102 for detecting a terahertz wave from the measurement object; a waveform acquisition unit for acquiring the time waveform of a terahertz wave by output from the detection unit; a housing 106 containing at least a part of a propagation path of a terahertz wave from the generation unit to the detection unit; a window unit 107 in the housing, the window unit having a permeability for a terahertz wave; and a mechanism 105 which moves in relative positions between the window unit and the parallel propagation region of a terahertz wave from the generation unit so that the propagation distance of the terahertz wave will change. The terahertz wave is emitted to the measurement object through the window unit, and information on the measurement object with the change compensated of the propagation distance of a terahertz wave generated by the movement of the reflective part of the measurement object outside or inside the parallel propagation region is acquired based on the time waveform acquired by the waveform acquisition unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to an apparatus for acquiring physical property or structure information of a measurement object using a terahertz wave, an acquisition method thereof, and the like. In particular, the present invention relates to a configuration using the principle of a device (THz-TDS device, THz-Time Domain Spectroscopy device) that measures terahertz waves in the time domain.

The terahertz wave is an electromagnetic wave having a component in an arbitrary frequency band in a range of 0.03 THz to 30 THz. In such a frequency band, there are many characteristic absorptions derived from the structures and states of various substances including biomolecules. Taking advantage of this feature, inspection techniques for non-destructive analysis and identification of substances have been developed. In addition, it is expected to be applied to safe imaging technology that replaces X-rays and high-speed communication technology. Furthermore, application to a tomography apparatus that visualizes the inside of a substance has attracted attention. This device is expected to visualize the internal structure at a depth of several hundreds of μm to several tens of mm, taking advantage of the characteristic of terahertz wave transmission.

Electromagnetic waves in this region have many characteristic absorptions related to atmospheric moisture. Therefore, in order to reduce the influence of the atmosphere, a device configuration is often used in which a portion where the terahertz wave propagates is isolated from the atmosphere and the atmosphere of the portion where the terahertz wave propagates is adjusted. In Patent Document 1, a measurement window that transmits terahertz waves is provided in a part of the casing used for isolation from the atmosphere in order to measure various measured objects without destroying the state of the adjusted atmosphere. An apparatus configuration for installing a measurement object is disclosed.

International Publication No. WO03 / 058212

As in the technique of Patent Document 1, the measurement object is fixed to the focal position of the terahertz wave in the form in which the measurement object is installed in the measurement window provided in a part of the housing containing the reflection measurement system. . For this reason, it is difficult to adjust the relative position of the focus position of the terahertz wave and the measurement object. For example, in the optical arrangement of FIG. 10 (b) that is also used in the description of the present invention, the following phenomenon has been confirmed as a result of the examination of the present inventors so far. In FIG. 10B, consider a case where the optical distance of the measurement object is measured from the time interval of the terahertz wave pulse reflected from the first interface 1018 and the second interface 1019 of the measurement object. Here, when the two interfaces are within the parallel propagation region 1022 and when one of the interfaces is in the light condensing process region 1021, the optical distance acquired by the apparatus changes. In other words, the measured value of the optical thickness of the measurement object may change depending on the position of the measurement object with respect to the focal position of the terahertz wave.

Here, the parallel propagation region 1022 is a region in which terahertz waves propagate in parallel, and this region corresponds to the depth of focus in terms of wave optics. In this specification, the parallel propagation region 1022 is also referred to as a focal position. The condensing process region 1021 is defined as a region in the process of collecting the terahertz wave.

In consideration of this phenomenon, as in Patent Document 1, in the apparatus configuration in which the position of the measurement object with respect to the focal position of the terahertz wave is fixed with respect to the measurement object installed in the apparatus housing, it is as follows. That is, when observing the surface or the internal structure of the measurement object, the optical distance measurement value may change depending on the location, and it may be difficult to accurately observe the structure of the measurement object. As a result, the measurement reliability of the device that acquires the internal structure may be reduced. In this specification, the optical distance that changes depending on the focal position of the terahertz wave is referred to as a secondary propagation distance.

In view of the above problems, acquires a time waveform with a time-domain spectroscopy, the information acquisition device of the present invention for obtaining information of the measurement object comprises a generator for generating a terahertz wave, a terahertz wave from the measurement object A detection unit that detects, a waveform acquisition unit that acquires a time waveform of a terahertz wave using the output of the detection unit, and a housing that includes at least a part of a propagation path of the terahertz wave from the generation unit to the detection unit And a terahertz wave from the window and the generator so as to change the propagation distance of the terahertz wave from the window disposed in the housing. A moving mechanism that moves the relative position of the parallel propagation region, and the terahertz wave from the generation unit is configured to be irradiated to the measurement object through the window , In the waveform acquisition unit Based on the obtained the time waveform, to obtain the information of said measured object change in the propagation distance of the terahertz wave is compensated reflecting portion is generated by moving the parallel propagation region and outside the of the measurement object.

  Further, in view of the above problems, an electromagnetic wave pulse is irradiated to a measurement object through a measurement window that is movably disposed in a housing that contains at least a part of the propagation path of the electromagnetic wave pulse, and the physical properties or structure of the measurement object The information acquisition method of the present invention for acquiring information includes the following steps. Generating electromagnetic pulses. Obtaining a time waveform of the electromagnetic wave pulse from the measurement window irradiated with the electromagnetic wave pulse; Obtaining a time waveform of an electromagnetic wave pulse from the measurement object irradiated with the electromagnetic wave pulse; Obtaining physical property information of a substance used for constructing a reconstructed waveform from a physical property database; Calculating a secondary propagation distance change of the electromagnetic wave pulse from information on a relative position between the focal position of the electromagnetic wave pulse and the measurement window; Using the time waveform of the electromagnetic wave pulse from the measurement object, the time waveform of the electromagnetic wave pulse from the measurement window, the change in the secondary propagation distance, and the physical property information as the reconstructed waveform Steps to build and optimize.

According to the present invention, since the apparatus uses a measurement window that is movable with respect to the housing that contains at least a part of the propagation path of the electromagnetic wave pulse, the terahertz wave is suppressed in a state in which the variation in the atmosphere in the housing is suppressed. It is possible to adjust the position of the focal point and the measurement object. As a result, accurate observation of the physical properties or structure of the measurement object is facilitated, and measurement reliability is improved.

FIG. 3 is a schematic configuration diagram of a device of the present invention described in the first and second embodiments. FIG. 3 is a diagram illustrating a configuration of a measurement window unit according to the first embodiment. FIG. 6 is a diagram for explaining a modification of the measurement window portion of the first embodiment. FIG. 10 is a diagram for explaining a modification of the measurement window part of the third embodiment. FIG. 6 is a diagram illustrating a configuration of a measurement window unit that holds an element according to a fourth embodiment. FIG. 6 is a diagram illustrating the configuration of a probe according to a fifth embodiment. FIG. 6 is a diagram for explaining an example of the operation flow of the apparatus of the second embodiment. FIG. 6 is a diagram for explaining the operation of the apparatus according to the second embodiment. The figure for demonstrating the transfer matrix used in a waveform reconstruction part. The figure explaining the problem of a prior art, and the data stored in a propagation distance database. 10A and 10B are diagrams illustrating an example of a display method of a display unit according to the second embodiment. FIG. 6 is a diagram for explaining a modification of the measurement window portion of the first embodiment. FIG. 10 is a diagram for explaining a modification of the measurement window part of the third embodiment.

The apparatus and method for acquiring the physical properties or structure of the measurement object according to the present invention is characterized in that the measurement window fixed to the housing in the conventional apparatus is movable. As a result, it is possible to adjust the focal position of the electromagnetic wave with respect to the position of the measurement object to be observed, thereby facilitating accurate observation of the physical properties or structure of the measurement object.

In the present invention, the physical properties and structure of the measurement object are observed by the electromagnetic wave pulse reflected by the measurement object. The electromagnetic wave pulse to be used only needs to have a certain degree of transparency with respect to the measurement object. Here, when the distance between the reflection parts of the measurement object is about several hundred μm to several tens of mm and it is desired to obtain physical properties from the reflection part to the reflection part, it is preferable to use a terahertz wave pulse. The terahertz wave pulse has a component in an arbitrary frequency band within a range of 0.03 THz to 30 THz. In this wavelength band, there are many characteristic absorptions derived from structures and states of various substances including biomolecules. By utilizing the transmissivity and analytical properties of the terahertz wave pulse, the apparatus and method of the present invention have an effect that not only information on the structure of the measurement object but also physical characteristics can be acquired. Therefore, in this specification, for example, information on whether or not a cell is an abnormal cell (such as a cancer cell) is also included in “information on physical properties or structure of measurement object”.

As described above, in this specification, the beam shape when the terahertz wave pulse is condensed is defined as follows. That is, the beam shape of the terahertz wave pulse condensed by the condensing means 1020 is considered by dividing it into a condensing process region 1021 and a parallel propagation region 1022 as shown in FIG. 10 (b). The parallel propagation region 1022 is a region where terahertz waves propagate in parallel, and this region corresponds to the depth of focus in terms of wave optics. In this specification, the parallel propagation region 1022 is also referred to as a focal position. The condensing process region 1021 is defined as a region in the process of collecting the terahertz wave. Further, a change in the propagation distance of the terahertz wave pulse accompanying a change in the relative position between the focal position of the terahertz wave pulse and the measurement object is simply referred to as a change in the propagation distance. In addition to this, as described above, the change in the optical propagation distance of the terahertz wave pulse caused by the measurement region deviating from the focal position of the terahertz wave pulse is sometimes referred to as a secondary change in the propagation distance. . Based on the definitions of these terms, the present invention will be described.

In the following, a more detailed description of embodiments of the present invention will be given. Here, description will be made using a terahertz wave pulse as the electromagnetic wave pulse.
(Embodiment 1)
The form which can implement the idea of the present invention is explained with reference to drawings. The configuration of an apparatus for acquiring the physical properties or structure of a measurement object in this embodiment will be described with reference to FIG. This apparatus includes a generation unit 101 that generates a terahertz wave pulse T ₁ and a detection unit 102 that detects a terahertz wave pulse T ₂ from a measurement object 108 as a part that handles the terahertz wave pulse.

Time waveform of the terahertz wave pulse T ₂ are, the time waveform by using a time-domain spectroscopy (Time Domain Spectroscopy method) are obtained. In order to acquire this time waveform, the apparatus has at least the following configuration. The apparatus has a light source 103 that outputs excitation light used to generate and detect terahertz wave pulses. The apparatus includes a delay optical unit 104 that adjusts the optical path length of the excitation light L ₂ from the light source 103 to the detection unit 102. The apparatus includes a waveform acquisition unit 109 that acquires the time waveform of the terahertz wave pulse T ₂ with reference to the change in the optical path length of the excitation light L ₂ defined by the delay optical unit 104 and the output of the detection unit 102. In addition, the apparatus includes a driving unit 105 used for generating the terahertz wave pulse T ₁ from the generating unit 101. The drive unit 105 is a voltage or current source. When the signal from the detection unit 102 is detected by a modulation / demodulation technique using a lock-in amplifier, the drive unit 105 may have a function of modulating the signal. The configuration of each part of the apparatus described so far may be a configuration that can acquire the time waveform of the terahertz wave pulse T ₂ as a result. For example, details of the configuration of each part are described in Japanese Patent Application No. 2012-047462 filed by the present applicant. In FIG. 1, M is a reflecting mirror, and BS is a beam splitter.

About the apparatus of this embodiment, the following structures differ from the conventional apparatus structure. In FIG. 1, the apparatus includes at least a part of a propagation path of a terahertz wave pulse from the generation unit 101 that generates an electromagnetic wave pulse to irradiate a measurement object to the detection unit 102, and can adjust an atmosphere surrounding the propagation path. It has a body 106. A measurement window 107 is movably provided in a part of the casing 106. The measurement window 107 is a part that is in the propagation path of the terahertz wave pulse and changes the propagation distance of the terahertz wave pulse. Specifically, the measurement window 107 is in the propagation path of the terahertz wave pulse, and includes a configuration of a measurement window movable to change the propagation path of the terahertz wave pulse from the generation unit 101 to the detection unit 102 It is. The measurement object 108 is disposed on the opposite side of the measurement window 107 from the propagation path of the terahertz wave pulse in the housing. With these configurations, the apparatus can adjust the position of the measurement object 108 outside the housing 106 with respect to the focal position of the terahertz wave while maintaining the atmosphere of the housing 106. The measurement window may be provided so as to be detachable, or can be prepared by the user.

Next, the detail of each part is demonstrated.
FIG. 2 is a diagram for explaining an embodiment of the measurement window 107. 2A is a perspective view of the measurement window 107, and FIG. 2B is a cross-sectional view of the AA ′ portion of the measurement window 107 shown in FIG. 2A. As shown in FIG. 2, the measurement window 107 is formed in a part of the housing 106. The measurement window unit 107 includes a measurement window 201, a measurement window housing 202, a sealing unit 204, and an actuator 205. The measurement window 201 is a part where the measurement object 108 is supported by the measurement window 107 and the terahertz wave pulse T ₁ is incident on the measurement object 108. The measurement window 201 also serves as a lid for suppressing fluctuations in the atmosphere adjusted by the housing 106. The measurement object 108 is in close contact with the measurement window 201, so that the interface between the measurement object 108 and the measurement window 201 is shaped along the shape of the measurement window 201. In other words, the shape of the measurement object 108 can be reshaped into a shape suitable for measurement. As a result, it is possible to suppress the scattering and interference of the terahertz wave pulse derived from the shape of the measurement object 108 and improve the measurement accuracy.

Since the measurement window 201 is disposed in the propagation path of the terahertz wave pulse, a material having excellent permeability to the terahertz wave pulse is preferable. For example, a resin such as polyethylene, Teflon (registered trademark), or a cycloolefin polymer can be applied. A porous form can also be applied to the resin material. Further, substrate materials such as high-resistance silicon, CVD (Chemical Vapor Deposition) diamond, and Z-cut quartz can be applied. The flatness of the measurement window 201 is desirably such that the terahertz wave pulse cannot recognize the structure. Specifically, the flatness of about 1 / 100λ to 1 / 20λ is desirable with respect to the effective wavelength λ of the terahertz wave pulse to be used (typically the center wavelength of the spectrum of the terahertz wave pulse). For example, when λ is 100 μm, the flatness of the measurement window 201 is desirably about 1 to 5 μm. Under this condition, the influence of scattering on the terahertz wave pulse from the measurement window 201 can be suppressed. Further, the flatness of the measurement window 201 also depends on the measurement resolution stored in the propagation distance database 111. For example, if the change in the propagation distance of the terahertz wave pulses are measured by the measurement capability of 100μm for the relative position between the focus position of the terahertz wave pulse T ₁ and the measuring window section 107, flatness, the measurement capability A smaller value is desirable. Further, when a measurement error is defined as the specification of the apparatus, the flatness is desirably a value smaller than this measurement error.

In addition, it is desirable that the measurement window 201 has a clear interface at a portion in contact with the measurement object 108. Therefore, depending on the physical properties of the measured object 108, the complex refractive index n _com of the measurement window 201 (in the following formula of this specification, the complex refractive index is indicated by n with an over-wave, but in the text, with an over-wave n (Represented simply by n _com ) may be added. For example, a configuration in which a liquid can be infiltrated into the whole or a part of the measurement window 201 for adjusting the refractive index can be considered. Specifically, a porous material made of a granular or sponge-like structure of polypropylene, polysulfone, nylon, or polyethersulfone having a high transmittance with respect to the terahertz wave pulse T ₁ can be used as the measurement window 201. As materials for adjusting the refractive index, water, physiological saline, oil, ionic water, formalin, phosphate buffer, alcohol, cell culture medium, sugar, hormone, protein, amino acid, and the like can be applied. These materials are desirably transparent to the terahertz wave pulse used. In addition, these materials may be used alone, or a plurality of materials may be mixed and used. In the above description, the measurement window 201 is described separately from the measurement object 108, but the measurement object 108 may also serve as the measurement window 201.

The measurement window housing 202 is a part that supports the measurement window 201 and changes the propagation distance of the terahertz wave pulse by moving the measurement window 201. In order to allow the terahertz wave pulse to reach the measurement window 201, the measurement window housing 202 is provided with an opening, and the measurement window 201 is supported by the opening. As shown in FIG. 2 (b), in this embodiment, a recess 203 is processed in the measurement window housing 202 as an opening. This is to prevent a part of the terahertz wave pulse incident on and reflected from the measurement window 201 from being blocked by the measurement window casing 202.

The measurement window housing 202 is disposed on the housing 106 via the actuator 205. In FIG. 2, the measurement window housing 202 moves in the normal direction with respect to the surface of the housing 106. FIG. 2 shows a form of the measurement window 107 to which the actuator 205 having a form in which the rod is expanded and contracted by a motor is applied. As a motor of the actuator 205, an actuator using a stepping motor, a linear motor, a piezo motor, or the like can be applied. Preferably, a non-rotating rod configuration is preferable so that the rotational force of the rod is transmitted to the measurement window casing 202 and the measurement window casing 202 does not rotate with respect to the moving direction. Although two actuators 205 are used in FIG. 2, the number used is not limited to this.

Further, these actuators 205 can be used as an inclination adjustment mechanism that adjusts the inclination of the measurement window 201 with respect to the moving direction of the measurement window 107. Specifically, when three actuators 205 are used, the inclinations of the measurement window casing 202 and the measurement window 201 can be adjusted with respect to the movement direction with respect to the pitch axis and the yaw axis. With this tilt adjustment mechanism, the reflection angle of the terahertz wave pulse T ₂ from the measurement window 107 can be adjusted. Therefore, compared to a configuration in which the measurement window 107 is fixed to the housing 106, terahertz wave alignment can be performed accurately, and the measurement accuracy of the apparatus is improved.

The reason why the measurement accuracy of the measurement object is improved if the terahertz wave alignment can be accurately performed will be described with an example. This is that of the above-mentioned patent application by the present applicant. Consider a case in which an electromagnetic wave pulse is irradiated on a measurement object, and physical properties of the measurement object including at least a first reflection part and a second reflection part are acquired by time domain spectroscopy. At the position where the waveform acquisition unit acquires the first pulse, the optical path length difference obtained by converting the time difference is adjusted by the delay unit, and a time waveform including at least the first pulse and the second pulse is acquired by time domain spectroscopy. . The adjustment amount of the measurement window monitored by the relative position monitoring unit and the acquired time waveform are stored. Then, the focusing position of the electromagnetic wave pulse with respect to the measurement object is finely moved. In this way, the position where the parallel propagation region, which is the condensing position of the electromagnetic wave pulse, overlaps the first reflecting part of the measurement object is calculated from the stored adjustment amount and the change in the time waveform, and the condensing position of the electromagnetic wave pulse is measured. Move to the first reflective part of the object. Obtain the first pulse from the time waveform when the parallel propagation region, which is the condensing position of the electromagnetic wave pulse, overlaps the first reflecting part of the object to be measured, and the adjustment amount Z _{1 of the} measurement window required for moving the condensing position acquiring an optical path length difference D ₁ by the delay unit in a position for obtaining the first pulse. Next, the converging position of the electromagnetic wave pulse is moved to the second reflecting part of the object to be measured, and the parallel propagation region that is the condensing position of the electromagnetic wave pulse is overlapped with the second reflecting part of the object to be measured. Get 2 pulses. Then, to obtain an optical path length difference D ₂ by the delay unit at a position acquired adjustment amount Z ₂ of the measuring window section required for the movement of the focusing position and the second pulse. After that, based on the adjustment amount change amount | Z ₂ −Z ₁ | and the optical path length difference change amount | D ₂ −D ₁ |, the first reflection portion and the second reflection portion of the measurement object The thickness and refractive index of the sandwiched region are calculated. In this way, even when the size of the region sandwiched between the reflecting portions of the measurement object is close to the size of the parallel propagation region of the electromagnetic wave pulse, the position of each reflecting portion can be accurately identified, and the first reflecting portion and the first reflecting portion can be identified. It is possible to improve the detection accuracy of the thickness and refractive index of the region sandwiched between the two reflecting portions. When a terahertz wave pulse is used as the electromagnetic wave pulse, the internal structure can be visualized and the physical properties can be identified at a depth of about several hundreds μm to several tens of mm by using the transparency of the terahertz wave pulse.

Returning to the description of FIG. The sealing unit 204 is disposed in a gap between the housing 106 and the measurement window housing 202. The sealing portion 204 is used to suppress a change in atmosphere adjusted by the housing 106. Since the sealing portion 204 is provided at a portion where the housing 106 and the measurement window housing 202 are in contact with each other, a low friction material such as fluororesin, nitrile rubber, silicon rubber, or high molecular weight polyethylene is preferable. A metal or resin containing a lubricant can also be applied.

FIG. 3 is a diagram for explaining a modified example of the measurement window unit 107. A difference from the measurement window 107 described with reference to FIG. 2 is an arrangement of actuators used for moving the measurement window casing 202. Specifically, the actuator 205 in FIG. 2 is inside the housing 106 and is fixed to the housing 106, but the actuator 305 in FIG. 3 is outside the housing 106. The actuator 305 includes a pressing member 307. The actuator 305 transmits the force of the actuator 305 to the measurement window casing 202 by pressing the pressing member 307 against the measurement window casing 202. As a result, the measurement window housing 202 moves. FIG. 3B is a cross-sectional view taken along AA ′ in FIG. As shown in the figure, the measurement window 107 has an expansion / contraction part 306. One end of the elastic part 306 is connected to a fixing part 309 provided in the housing 106. For example, a tension coil spring can be applied to the stretchable portion 306. The measurement window casing 202 is disposed on the casing 106 via the expansion / contraction section 306 by the pulling force of the expansion / contraction section 306. More specifically, the measurement window housing 202 moves and is arranged at an arbitrary position by a balance between the force applied from the actuator 305 and the force by which the expansion / contraction part 306 lifts the measurement window housing 202.

FIG. 3 (c) is a modification of FIG. 3 (b). Specifically, the configuration of the portion where the measurement window casing 202 is arranged in the casing 106 is different. As shown in FIG. 3 (c), the measurement window housing 202 is fixed to the housing 106 by an extendable portion 306 and a guide screw 308. Specifically, the guide screw 308 is movable along the depth direction of the guide hole 310 provided in the housing 106, and the measurement window housing 202 is fixed to the housing 106 by the force of the extendable part 306. For example, a compression coil spring or a disc spring can be applied to the expansion / contraction part 306. The expansion / contraction part 306 is disposed between the measurement window casing 202 and the guide hole 310, and the guide screw 308 is inserted into the central part of the expansion / contraction part 306.

In general, the configuration of an actuator having a motor is large, but in the configuration of FIG. 3, this actuator can be arranged outside the housing 106. Therefore, the area occupied by the components arranged inside the housing 106 can be reduced, and the volume inside the housing 106 can be reduced. As a result, the time required for adjusting the atmosphere inside the housing 106 can be shortened, and the apparatus can be easily downsized. Further, by using the expansion / contraction part 306 for the measurement window part 107, it is possible to absorb vibration from the outside. When unnecessary vibration occurs, the position of the measurement window 107 changes, the propagation distance of the terahertz wave pulse changes, and the measurement accuracy may decrease when acquiring the time waveform of the terahertz wave pulse. By absorbing this unnecessary vibration, the measurement accuracy of the apparatus can be stabilized.

In the configuration of the measurement window 107 in FIG. 2, an actuator 205 that supports the measurement window housing 202 is used as the tilt adjustment mechanism. On the other hand, in the configuration of the measurement window 107 in FIG. 3, an actuator 305 provided outside the housing 106 is used as the tilt adjustment mechanism. In particular, the actuator 305 has a mechanism for adjusting the inclination of the pressing member 307, by pressing the pressing member 307 to the measurement Madokatamitai 202 while maintaining the inclination of the pressing member 307, the reflection of the terahertz wave pulse T ₂ The angle can be adjusted.

2 and 3, the actuators 205 and 305 used to move the measurement window housing 202 are used as an inclination adjustment mechanism for adjusting the inclination of the measurement window 201 with respect to the movement direction of the measurement window 107. doing. However, the measurement window 107 may have this tilt adjustment mechanism independently. For example, FIG. 12 shows an example of a form in which the tilt adjustment mechanism is made independent in the measurement window unit 107. In FIG. 12, the configuration necessary for moving the measurement window casing 202 is omitted in the measurement window 107, but in reality, the mechanism necessary for moving the measurement window 107 described above can be applied. .

12A is a top view of the measurement window 107, FIG. 12B is an AA ′ sectional view of the measurement window 107, and FIG. 12C is a BB ′ sectional view of the measurement window 107. The difference from the conventional measurement window unit 107 is that an inclination adjustment plate 1209 for adjusting the inclination of the measurement window 201 is provided. Specifically, as shown in FIG. 12B, the inclination adjustment plate 1209 is fixed to the measurement window housing 202 with a guide screw 308. The tilt adjustment plate 1209 has a guide hole 310, and the guide screw 308 moves in the depth direction of the guide hole 310. The expansion / contraction part 306 is disposed between the end of the inclination adjusting plate 1209 and the guide screw 308. The guide screw 308 is inserted into the central portion of the expansion / contraction part 306, and the tilt adjustment plate 1209 is pressed against the measurement window housing 202 by the force of the expansion / contraction part 306. A compression spring or a disc spring can be applied to the expansion / contraction part 306. The sealing unit 1204 is inserted between the inclination adjustment plate 1209 and the measurement window casing 202, and suppresses fluctuation of the atmosphere adjusted by the casing 106. An O-ring can be applied to the sealing portion 1204. Preferably, since the sealing portion 1204 is deformed by a force applied from the inclination adjusting plate 1209, the material used for the sealing portion 1204 is preferably a material with low hardness. As a result, since the sealing portion 1204 is deformed along the inclination of the inclination adjusting plate 1209, the sealing state is maintained and the variation in the atmosphere is reduced.

Further, as shown in FIG. 12C, the inclination adjusting plate 1209 has a screw bushing 1211 and an adjusting screw 1210. The end of the adjustment screw 1210 is abutted against the measurement window housing 202. The distance between the measurement window casing 202 and the tilt adjustment plate 1209 is adjusted by the amount of pressing of the adjustment screw 1210. In the configuration of the measurement window unit 107 in FIG. 12A, the three adjustment screws 1210 can be used to adjust the inclination of the measurement window 201 with respect to the movement direction with respect to the pitch axis and the yaw axis. With this tilt adjustment mechanism, the reflection angle of the terahertz wave pulse T ₂ from the measurement window 107 can be adjusted. Therefore, compared to a configuration in which the measurement window 107 is fixed to the housing 106, terahertz wave alignment can be performed accurately, and the measurement accuracy of the apparatus is improved.

According to the apparatus of the present embodiment, since the apparatus has the measurement window 107 that is movable with respect to the casing 106 that adjusts the atmosphere, the focal position of the terahertz wave is suppressed in a state where the adjusted atmosphere is suppressed. And the position of the measured object 108 can be adjusted. As a result, measurement can be performed in the parallel propagation region 1022 (see FIG. 10B) where the terahertz wave pulse propagates in parallel, which facilitates accurate observation of the surface or internal structure of the measurement object and improves the reliability of the apparatus. .

(Embodiment 2)
As a technique for acquiring the physical properties of the measured object 108, there is a technique for reconstructing the response of a terahertz wave pulse by using a transfer matrix (see, for example, Proceedings of SPIE, Vol. 5692, 241-254 (2005)). The measurement object information acquisition apparatus according to the present embodiment is an application of the apparatus according to the first embodiment to an apparatus that acquires physical properties of the measurement object 108 using a transfer matrix. In addition, the description of the part which is common in the above description is abbreviate | omitted.

The apparatus of this embodiment will be described with reference to FIG. The apparatus of the present embodiment has the following configuration added to the configuration of the apparatus of the first embodiment. The relative position monitoring unit 110 is a part that monitors the relative position between the focal position of the terahertz wave pulse T ₁ and the measurement window unit 107. The propagation distance database 111 includes information used for calculating the change dL of the secondary propagation distance of the terahertz wave pulse caused by the change in the arrangement of the optical system existing in the propagation path of the terahertz wave pulse with respect to the relative position. This is the output part. More specifically, the influence of the positional relationship between the focal position of the measuring window 201 and the terahertz wave pulse T ₁ constituting the measuring window section 107 on the propagation distance of the terahertz wave pulses are stored.

FIG. 10 is a diagram for explaining an example of data stored in the propagation distance database 111. FIG. 10 (b) is a diagram for explaining data stored in the propagation distance database 111. FIG. In FIG. 10 (b), the measurement window 201 has an interface whose refractive index changes at the boundary with the outside, and is here referred to as a first interface 1018 and a second interface 1019. The terahertz wave pulse is condensed on the measurement window 201 by the condensing means 1020. At this time, the interval between the light collecting means 1020 and the measurement window 201 is defined as a relative position 1023. When the time waveform of the terahertz wave pulse reflected from the measurement window 201 is measured, reflected waves from the first interface 1018 and the second interface 1019 can be observed. The time interval Δt of the reflected wave is a value reflecting the optical distance of the measurement window 201 in FIG. 10 (b). As described in the section of “Problems to be Solved by the Invention”, the optical distance (secondary propagation distance) of the measurement window 201 to be observed depends on the positional relationship between the focal position of the terahertz wave pulse and the measurement window 201. ) Has been confirmed to change.

FIG. 10A is a graph plotting the time interval Δt of the terahertz wave pulse reflected from the measurement window 201 when the relative position 1021 is changed. In the propagation distance database 111, these pieces of information are stored for each material used. The graph shown in FIG. 10 (a) is a plot of information when a 30 μm thick porous film is used as the measurement window 201. The time interval Δt of the terahertz wave pulse described in the graph can be converted into the propagation distance of the terahertz wave pulse by using the light velocity c and the physical property value of the measurement window 201. Here, as shown in FIG. 10 (b), the state where the first interface 1018 of the measurement window 201 is in the condensing process region 1021 and the second interface 1019 is in the parallel propagation region 1022 corresponding to the focal position is measured. The initial position of the window 201 is defined as 0 mm. This position is determined by the measurer. For example, the initial position is converted to 0 mm as a reference, but the measured value of the relative position 1023 may be plotted without conversion. According to the graph of FIG. 10 (a), as the relative position 1023 increases, the time interval Δt of the terahertz wave pulse decreases, and when the relative position 1023 exceeds 1 mm, the time interval Δt shows a substantially constant value. It was done. And when relative position 1023 exceeded 1.6 mm, the tendency for time interval (DELTA) t to become large again was confirmed. From this result, for example, the parallel propagation region 1022 corresponding to the focal position can be defined as 1.0 mm to 1.6 mm with respect to the relative position 1023. In other words, in the case of the example shown here, it can be seen that the parallel propagation region 1022 corresponding to the focal position has a region of about 0.6 mm inside the measurement window 201. When the physical property of the measurement window 201 is known, it can be converted into a region in free space. As described above, even with a material having the same shape, the optical propagation distance of the terahertz wave pulse changes depending on the relationship between the focal position of the terahertz wave pulse and the position where the measurement object is arranged. Specifically, when the measurement target is at the focal position of the terahertz wave pulse, the optical propagation distance of the terahertz wave pulse depends on the physical properties of the measurement target. However, when the object to be measured is displaced from the focal position of the terahertz wave pulse, the optical propagation distance of the terahertz wave pulse is not only the physical properties of the object to be measured, but also the change caused by the optical system (secondary propagation). Equivalent to distance) is added. That is, it can be seen that the secondary propagation distance of the terahertz wave pulse varies depending on the focal position of the terahertz wave pulse and the position of the measurement object.

The data stored in the propagation distance database 111 shown here is data of a certain thickness, but the following data format may be used in order to improve versatility. For example, the trend of the change in the time interval of the reflected terahertz wave pulse with respect to the change in the thickness of the material or the change in the size of the parallel propagation region 1022 felt by the material may be calculated from the actual measurement data regarding the material having a plurality of thicknesses. By using such a propagation distance database 111, the range in which the propagation distance database 111 can be applied can be expanded, so the versatility of the apparatus and method is expanded.

In addition, regarding the time waveform of the terahertz wave pulse acquired by the waveform acquisition unit 109, the position change of the peak value of the time waveform of the terahertz wave pulse accompanying the movement of the reflection interface existing in the atmosphere (free space) is stored in the propagation distance database 111. It may be stored. Utilizing this data, for example, by calculating the difference between the peak values of the two reflection interfaces, the time interval Δt of the terahertz wave pulse at a certain relative position 1023 can be calculated. Then, in a state where the spacing between the reflective interfaces is maintained, it is possible to select data to be used so that the relative position 1023 changes, and to obtain a graph approximated to FIG. it can. This graph corresponds to plotting the change in the propagation distance with respect to the change in the focal position of the terahertz wave pulse for a material having a complex refractive index n _com of 1 and a thickness determined by the measurer. By using this data and multiplying by an arbitrary complex refractive index n _com , the propagation distance database 111 shows a change in secondary propagation distance of a terahertz wave pulse for a material of an arbitrary thickness and a complex refractive index n _com. Can be output. By using such a propagation distance database 111, the range in which the propagation distance database 111 can be applied can be expanded, so the versatility of the apparatus and method is expanded.

When measuring the measurement object 108 arranged in the measurement window 201, if the point to be observed of the measurement object 108 is at the focal position, the terahertz wave pulse can be regarded as a parallel beam, so that the measurement accuracy of the optical distance is maintained. it can. However, when a part of the measurement object 108 to be observed exists in the condensing propagation region 1021, the secondary propagation distance of the terahertz wave pulse changes. As described above, this change in the secondary propagation distance is defined as a change originating from the optical system rather than the physical property of the measurement object, and expressed as a change dL in the secondary propagation distance of the terahertz wave pulse. Such a change dL in the secondary propagation distance of the terahertz wave pulse may cause a measurement error depending on the measurement conditions, so it is desirable to deal with it. The method of the present invention described later includes a method for suppressing this error.

Returning to the description of FIG. The physical property database 112 is a part in which the identification name of the substance and information on the physical property of the substance are stored. Examples of the physical properties to be stored include a complex refractive index n _com , an absorption coefficient α, a transmittance, and a reflectance. Preferably, a frequency distribution of physical properties in a frequency region to be measured is stored.

The waveform acquisition unit 109 is the same as that of the first embodiment described above. The waveform acquisition unit 109 outputs the measurement waveform E _meas (t) from the measurement object 108. The waveform reconstruction unit 113 is a part for constructing a reconstructed waveform E _rec (t) using the change dL of the propagation distance of the terahertz wave pulse obtained from the propagation distance database 111 and the physical property information stored in the physical property database 112. It is. Specifically, the complete reflection waveform of the terahertz wave from the measurement window unit 107 is set as a reference waveform E _ref (t). Using this reference waveform E _ref (t), information in the propagation distance database 111 and the physical property database 112, a reconstructed waveform E _rec (t) approximated to the measured waveform E _meas (t) is calculated and constructed. This calculation expresses the propagation of electromagnetic waves as a transfer matrix, and calculates the reconstructed waveform E _rec (t) by optimizing the transfer matrix. The physical property of the measured object 108 is acquired using the value of the variable of the transfer matrix obtained by optimizing the reconstructed waveform E _rec (t).

The operation of the waveform reconstruction unit 113 will be described with reference to the drawing. FIG. 9 is a diagram for explaining a transfer matrix used in the waveform reconstructing unit 113. FIG. 9 (a) is a diagram for explaining a transfer matrix for an object layer. FIG. 9 (b) is a diagram for explaining a transfer matrix for the interface between objects. FIG. 9 (c) is a diagram for explaining a transfer matrix in the form of a plurality of layers and interfaces. Here, the transfer matrix for the mth layer is A ^(m), and the transfer matrix for the mth interface is B ^(m) . Let M be the transfer matrix of the m layer. In the figure, E ₍₊₎ indicates a traveling wave, and E _(-) indicates a backward wave. In describing the transfer matrix M used in the waveform reconstruction unit 113, the complex refractive index n _com and the absorption coefficient α of the object are defined as follows.

Here, n is the refractive index, κ is the extinction coefficient, c is the speed of light, ν is the frequency, and k is the wave number. The wave number k is expressed by the following equation (3).

At this time, the traveling wave E ₍₊₎ and the backward wave E ₍₋₎ are defined as follows.

Here, t is time and x is a position vector.

A transfer matrix used in the present embodiment will be described with reference to FIG. The measurement object is assumed to have multiple layers. In FIG. 9 (a) illustrating the transfer matrix of the mth layer for the measurement object, the thickness of the _mth layer is dm. Then, the refractive index of the m-th layer, the wave number, representing the absorption coefficient n _com-m, k _m, and alpha _m. E ₍₊₎ 'and E _(-) ' are forward and backward waves after propagating through the layer. In Fig. 9 (a), E ₍₊₎ 'and E _(-) ' are given by the following equation, based on the propagation direction of electromagnetic waves from E ₍₊₎ (ν) to E ₍₊₎ '(ν) .

At this time, if the transfer matrix of the m-th layer is A ^(m) in FIG. 9 (a), A ^(m) is expressed as follows from equations (5) and (6).

As can be seen from Equation (7), the transfer matrix A ^(m) represents the attenuation and phase change of the electromagnetic wave when propagating through the layer. FIG. 9 (b) is a diagram illustrating the transfer matrix of the mth interface for the measurement object. Specifically, the interface between the layer m and the layer m + 1 is defined as the mth boundary. In the figure, the transfer matrix of the mth interface is B ^(m) . At this time, when the electromagnetic wave propagates from the layer m to the layer m + 1, the complex amplitude transmittance t _{m, m + 1} and the complex amplitude reflectivity r _{m, m + 1 at the mth} boundary are as follows: expressed.

At this time, the relationship between E ₍₊₎ , E ₍₋₎ , E ₍₊₎ ′, and E ₍₋₎ ′ in FIG.

Further, in FIG. 9 (b), if the transfer matrix at the m-th interface is B ^(m) , B ^(m) is expressed as follows from equations (10) and (11).

Equation (12) can be modified as follows using equations (8) and (9).

As shown in Equation (13), the transfer matrix B ^(m) of the m-th interface can be simply expressed by the complex refractive index of the material in contact with the interface. As shown in FIG. 9 (c), when the transfer matrix when the measurement object is formed of a plurality of layers is M, the transfer matrix M is expressed as a product of the transfer matrix of each layer and each interface.

As a result, the traveling wave E ₍₊₎ and the backward wave E ₍₋₎ can be expressed as follows using the transfer matrix M.

As described above, the waveform reconstruction unit 113 measures the full reflection waveform of a terahertz wave with a reference waveform E _ref (t) from the window portion 107, the reference waveform E _ref (t) measured waveform E _meas (t using The reconstructed waveform E _rec (t) approximated to) is calculated. When the apparatus configuration is such that the reflected terahertz wave pulse from the measurement object 108 is measured as shown in FIG. 1, the traveling wave E ₍₊₎ is information in the frequency domain of the reference waveform E _ref (t). The backward wave E ₍₋₎ is information in the frequency domain of the reconstructed waveform E _rec (t). In this embodiment, the frequency domain information of the backward wave E ₍₋₎ is converted into time domain information, compared with the measured waveform E _meas (t), and the transfer matrix M is optimized. Specifically, the complex refractive index and thickness of each layer are optimized. When the transfer matrix is optimized, if the surface or part of the internal structure of the measurement object 108 is known, this known information may be acquired with reference to the physical property database 112. In addition, when there are candidates for information on the surface or internal structure of the measurement object 108, the range of parameters to be optimized may be limited with reference to the physical property information of the candidates.

As described above, the secondary propagation distance of the terahertz wave pulse changes depending on the relationship between the focal position of the terahertz wave pulse and the arrangement position of the measurement object. For example, in FIG. 9 (c), even if the physical properties of the portion corresponding to the transfer matrix A ⁽¹⁾ and the physical properties of the portion corresponding to A ⁽²⁾ are the same, the propagation distance of the terahertz wave pulse depends on the focal position of the terahertz wave pulse. Will change. For example, consider a case where the focus of the terahertz wave pulse exists in a portion corresponding to the transfer matrix A ⁽¹⁾ and the portion corresponding to the transfer matrix A ⁽²⁾ is deviated from the focus. In this case, the propagation distance of the portion corresponding to the transfer matrix A ⁽²⁾ is longer than the propagation distance of the portion corresponding to the transfer matrix A ⁽¹⁾ . If the physical properties of each part are calculated ignoring this effect, the physical properties of the part corresponding to the transfer matrix A ⁽¹⁾ and the part corresponding to the transfer matrix A ⁽²⁾ may be calculated as different results even for the same material. There is. In order to suppress this influence, the waveform reconstruction unit 113 of the present embodiment uses a transfer matrix C ^(m) related to the following layers in combination with the transfer matrix A ^(m) as appropriate.

The difference from the transfer matrix A ^(m) is that the change in the secondary propagation distance of the terahertz wave pulse in the time domain is the phase change φ _m in the frequency domain. The phase change φ _m is expressed by the following equation.

dL _m is the optical path length change of the terahertz wave pulse in the m-th layer material. The total secondary propagation distance change dL of the terahertz wave pulse can be expressed by adding the optical path length change dL _m in each layer as in the following equation.

The waveform reconstruction unit 113 refers to the output of the relative position monitoring unit 110, and calculates the secondary propagation distance change dL _m of the terahertz wave pulse of each layer using the data stored in the propagation distance database 111. The dL _m used in the equation (17) can be selected as follows depending on the material conditions corresponding to the transfer matrix C ^(m) . When the material corresponding to the transfer matrix C ^(m) is known or can be estimated, the change in the optical path length of the terahertz wave pulse is obtained by utilizing the actually measured data as shown in FIG. 10 (a).

Here, dL _{material_m} is a value of a change in secondary propagation distance of the terahertz wave pulse in the known or estimated _material of the m-th layer. The secondary propagation distance change dL _{material_m} of the terahertz wave pulse is calculated by the waveform reconstruction unit 113 using information in the propagation distance database 111. Desirably, dL _{material_m} uses actual measurement data (that is, measurement results of a material having the same physical properties and shape as the measurement object). When the measurement conditions of the data in the propagation distance database 111 (for example, the thickness of the material) and the measurement conditions at the time of analysis with the transfer matrix C ^(m) are greatly different, the following can be performed. That is, as described above, the value estimated from the measurement data under a plurality of measurement conditions stored in the propagation distance database 111 can be used as the dL _{material_m} . By using the actual measurement data, it is possible to increase the speed of optimization by limiting the calculation amount of the waveform reconstruction 113, and to improve the reliability of the apparatus.

When using a secondary change in propagation distance in the atmosphere (free space) as data stored in the propagation distance database 111, dL _m is expressed by the following equation.

Here, dL _{air_m} is the value of the change in the secondary propagation distance of the terahertz wave pulse when the atmosphere (free space) is assumed for the m-th layer material. Actually, as described above, dL _{air — m} is calculated using the thickness _dm used in the transfer matrix C ^(m) . The change in the secondary propagation distance of the terahertz wave pulse can be applied to various forms of materials by estimating using the parameters of the transfer matrix output in the optimization process. As a result, the versatility of the device is increased.

As described above, the transfer matrix C ^(m) is used in place of the transfer matrix A ^(m) at a location where the correction of the secondary propagation distance of the terahertz wave pulse is necessary. For example, a measurement object 108 having a two-layer structure is measured in close contact with the measurement window 201, and a change in the secondary propagation distance of the terahertz wave pulse derived from the optical system of the apparatus is added to the measurement window 201. If necessary, equation (14) changes as:

Here, m = 1 corresponds to the measurement window 201, and m = 2, 3 corresponds to the structure inside the measurement object 108. Further, when the backward wave from the material can be ignored as in the case of a material having a large absorption such as a living body or a material having a sufficient thickness, the equation (15) is expressed as the following equation.

Further, when the material boundary can be regarded as a mirror surface that reflects electromagnetic waves, the equation (14) is expressed as the following equation. Here, the mirror surface exists in the m layer.

The transfer matrix I (omitted, but after A ^{(m) in} Equation (14)) is a unit matrix. Then, using this transfer matrix M ″, equation (15) is expressed as follows.

The meaning of equation (24) is that the electromagnetic wave is completely reflected on the mirror surface of the material, so that the traveling wave and the backward wave are regarded as the same. As a result, the effect of the transfer matrix B ^(m) on the interface corresponding to the mirror surface is included by setting E ' _(-) = E' ₍₊ ^). Can be ignored.

Using the transfer matrix as described above, the waveform reconstruction unit 113 optimizes the transfer matrix and calculates a reconstructed waveform E _rec (t) approximate to the measured waveform E _meas (t). Specifically, the frequency domain information is converted into the time domain, and the measured waveform E _meas (t) is compared with the reconstructed waveform E _rec (t). Here, the initial value of the transfer matrix is determined with reference to the physical property database 112. For example, when a physical property candidate is selected, the physical property value is input as an initial value. Further, the range of each variable of the transfer matrix to be optimized can be determined by referring to the candidate material shown in the physical property database 112. Through these steps, when the waveform reconstruction unit 113 calculates the reconstructed waveform E _rec (t), each variable of the transfer matrix is prevented from converging to an abnormal value, and the reliability of the apparatus is improved. be able to.

The display unit 114 is a part that receives the calculation result of the waveform reconstruction unit 113 and displays the calculation result. The display method displays the physical properties of the measured object 108 using the variables used in the calculation. Further, the measurement object 108 may be specified by comparing the physical property data stored in the physical property database 112 and the calculation result of the waveform reconstruction unit 113. Further, in the case where the apparatus is in the form of an apparatus that acquires a tomographic image of the measurement object 108, it may be displayed in different colors according to the physical properties distributed in the tomographic image. The display unit 114 is a part corresponding to the user interface, and is constructed in accordance with the demands of the measurer. Therefore, the display form is not limited to these.

According to the apparatus of the present embodiment, the reconstructed waveform E _rec (t) approximated to the measurement waveform E _meas (t) measured by the apparatus is constructed from the reference waveform E _ref (t) and the physical property information of the physical property database 112. In this case, the propagation distance change dL of the terahertz wave pulse is taken into consideration. As a result, the accuracy of calculation of the reconstructed waveform E _rec (t) is improved.

The method of the apparatus will be described with reference to the drawings. FIG. 7 is a diagram illustrating an example of an operation flow of the apparatus. FIG. 8 is a diagram for explaining the operation of this apparatus. When the operation of the apparatus is started, the waveform acquisition unit 109 refers to the adjustment amount of the delay optical unit 104 and the output of the detection unit 102, and acquires the reference waveform E _ref (t) from the measurement window unit 107 (S701). The waveform acquisition unit 109 performs Fourier transform on the acquired reference waveform E _ref (t), converts it to frequency information E _ref (ν), and outputs it to the waveform reconstruction unit 113 (S702). At this time, the measurement window 201 constituting the measurement window unit 107 is replaced with a reflector 801 that reflects the terahertz wave pulse as shown in FIG. 8 (a). Therefore, the terahertz wave pulse T ₁ incident on the reflector 801 and the terahertz wave pulse T ₂ from the reflector 801 are the same. In FIG. 8, a dial gauge is used as the relative position monitoring unit 110. When it is desired to monitor the relative position without contact, a laser displacement system or the like can be applied. The relative position monitoring unit 110 uses the position of the measurement window 107 when the reference waveform E _ref (t) is acquired (the position of the measurement window housing 202 in the example of FIG. 8) as the initial position L _ref of the measurement window 107. The data is output to the optical path length database 111 (S703). Data obtained in the steps S701 to S703 need not be measured for each measurement, and may be acquired in advance.

As shown in FIG. 8B, a measurement window 201 is installed in the measurement window unit 107 instead of the reflector 801. The measurement object 108 is disposed on the opposite side of the measurement window 107 from the propagation path of the terahertz wave pulse. Specifically, the measurement object 108 is disposed in close contact with the measurement window 201. As a result, the terahertz wave pulse T ₂ has a time waveform that takes into account the information of the measurement window 201 and the measurement object 108. The measurer adjusts the focal position of the terahertz wave pulse T ₁ in accordance with the shape and properties of the measurement window 201 and the place where the measurement object 108 is desired to be observed. In particular, the case of FIG. 8 (b), adjusting the focal position of the terahertz wave pulse T ₁ for measuring window 201 and workpiece 108 by adjusting the position of the measuring Madokatamitai 202 constituting the measuring window 107 . The relative position monitoring unit 110 (in the example of FIG. 8 the position of the measurement Madokatamitai 202) position L _meas the measuring window 107 after the focus position adjustment of the terahertz wave pulses T ₁ and outputs to the optical path length database 111 (S704 ). The change in the propagation distance of the terahertz wave pulse accompanying the movement of the measurement window 107 can be converted from information on the incident angles of L _ref -L _meas and the terahertz wave pulse T ₁ .

The waveform acquisition unit 109 acquires the measurement waveform E _meas (t) from the measurement object 108 through the measurement window 201 with reference to the adjustment amount of the delay optical unit 104 and the output of the detection unit 102 (S705). The waveform acquisition unit 109 performs a Fourier transform on the acquired measurement waveform E _meas (t), converts it to frequency information E _meas (ν), and outputs it to the waveform reconstruction unit 113 (S706). In constructing the reconstructed waveform E _rec (t), the waveform reconstructing unit 113 defines the structure of the measurement object 108 (S707). More specifically, the measurement window 201 and the measurement object 108 are regarded as one measurement object, and the transfer matrix M used by the waveform reconstruction unit 113 is defined. The waveform reconstructing unit 113 acquires parameters of known parts from the physical property database 112 for the parameters of each transfer matrix (S708). Here, although the parameters to be used are not known, when the material is narrowed down to some extent, the parameter area can be set with reference to the physical property database 112. When the physical properties constituting the measurement target are unknown, the measurer sets initial values of unknown parameters.

The waveform reconstruction unit 113 refers to the position information of the measurement window unit 107 output from the relative position monitoring unit 110, and calculates the secondary propagation distance change dL of the terahertz wave pulse (S709). Then, the waveform reconstructing unit 113 calculates the reconstructed waveform E _rec (t) in the time domain using each parameter of the transfer matrix (S710). Then, the waveform reconstruction unit 113 uses the measurement waveform E _meas (t) as a comparison target, and uses the reference waveform E _ref (t), the secondary propagation distance change dL, and the physical property value to reconstruct the waveform E _rec ( t) is optimized (S711). Specifically, the parameters of the transfer matrix used for waveform reconstruction are optimized.

When the apparatus or the measurer determines that the calculation of optimization of the reconstructed waveform E _rec (t) is necessary again, the process returns to S707. For example, when the coincidence between the measured waveform E _meas (t) and the reconstructed waveform E _rec (t) is low and it is necessary to try a transfer matrix M having a different structure, recalculation is performed. If an abnormal value is included in the calculation result of the transfer matrix, recalculation is attempted.

According to this method, when the reconstructed waveform E _rec (t) is optimized, the optimization is performed in consideration of the secondary propagation distance change dL of the terahertz wave pulse. As a result, the accuracy of optimization of the reconstructed waveform E _rec (t) is improved.

When collating the measured object 108 using each parameter of the calculated transfer matrix, compare the physical property value used to construct the reconstructed waveform E _rec (t) with the physical property value of the substance stored in the physical property database 112 Then, the substance constituting the measurement object 108 is determined (S712). According to this method, the physical property value is obtained from the reconstructed waveform E _rec (t) in consideration of the secondary propagation distance change dL of the terahertz wave pulse. For this reason, the accuracy of the physical property value obtained is improved as compared with a form in which the secondary propagation distance change dL is not taken into consideration. As a result, the accuracy in determining the substance constituting the measurement object 108 by comparing the physical property values is improved. That is, the accuracy in determining the substance constituting the measurement object is improved by comparing the physical property value used for constructing the reconstructed waveform with the physical property information stored in the physical property database.

The results output in the above steps are presented to the measurer by the display unit 113. In the description so far, the time waveform of the terahertz wave pulse T ₂ obtained by the waveform acquisition unit 109 and the waveform reconstruction unit 113 corresponds to an A-scan tomographic image. In the case of this embodiment, when it is desired to obtain a B-scan tomographic image (tomographic image) or a three-dimensional tomographic image, it can be realized by scanning the measurement object 108 with the terahertz wave pulse T ₁ . Specifically, these images can be realized by scanning the terahertz wave pulse T ₁ in a one-dimensional direction or a two-dimensional direction on a plane including a vector normal to the moving direction of the measurement window 107. The display unit 113 also displays these images.

FIG. 11 (a) is a schematic diagram of a measurement object and its tomographic image. Here, a B-scan tomographic image is shown. Visualizing the time waveform obtained from the waveform acquisition unit 109 changes the propagation speed of the terahertz wave pulse due to the difference in physical properties of each part constituting the measurement object, so that the propagation length of the terahertz wave pulse in each part differs. FIG. 11 shows an example of skin composed of cancer tissue, epidermis, and dermis as a measurement object. As a result, when the information of the waveform acquisition unit 109 is visualized, the position of the interface partially changes compared to the cross-sectional structure of the measurement object, as in the tomographic image of FIG. 11 (a). At this time, in the waveform reconstruction unit 113, the first feature region 1124, the second feature region 1125, and the third feature region 1126 are defined as the structure of the measurement object 108, and by optimizing the transfer matrix, The physical properties of each region can be determined. Here, in FIG. 11, a region sandwiched between the outermost surface of the epidermis and the interface between the epidermis and the dermis is defined as a first feature region 1124 as the feature region. A region sandwiched between the outermost surface of the cancer tissue and the interface between the cancer tissue and the dermis is a second feature region 1125. A region sandwiched between the interface between the epidermis and the dermis and the interface between the dermis and the subcutaneous tissue is defined as a third feature region 1126. As shown in FIG. 11B, the display unit 113 refers to the physical properties of each feature region, adjusts the size of each feature region of the tomography image, and acquires an image close to the measurement object. At this time, according to the physical properties of each feature area, the display form of the feature area is changed and presented. For example, the color can be changed for each feature region.

(Embodiment 3)
Another embodiment in which the idea of the present invention can be implemented will be described with reference to the drawings. Specifically, this is a modification of the measurement window 107. Descriptions of parts common to the above description are omitted.

The measurement window unit 107 described in the first embodiment is a form in which the measurement window 201 is fixed to the measurement window housing 202 constituting the measurement window unit 107. Therefore, as in the second embodiment, in order to acquire a multidimensional tomographic image, it is necessary to scan the terahertz wave pulse T ₁ on the measurement object 108 installed in the measurement window 201. In the present embodiment, a measurement window 107 capable of acquiring a multidimensional tomographic image by moving the measurement object 108 installed in the measurement window 107 is provided in this embodiment.

FIG. 4 shows the configuration of the measurement window 107 of the present embodiment. The difference from the configuration of the measurement window unit 107 so far is that the measurement window casing 202 is configured by a first measurement window casing 407 and a second measurement window casing 408. The first measurement window casing 407 is a part that moves the measurement window 201 in a direction in which the propagation distance of the terahertz wave pulse is changed. In FIG. 4, the first measurement window casing 407 is supported by the actuator 205. However, as described with reference to FIG. In this case, the first measurement window housing 407 is moved by the actuator 305 provided outside the housing 106. The second measurement window casing 408 supports the measurement window 201 and is disposed on the first measurement window casing 407. Second measurement window casing 408 is scanned in a one-dimensional direction or a two-dimensional direction by a stage (not shown) with respect to a plane including a vector in the normal direction with respect to the direction in which the propagation distance of the terahertz wave pulse changes. . As a result, a multidimensional tomographic image such as a tomographic image (tomographic image) of a scan or a three-dimensional tomographic image can be acquired. The stage (not shown) described here may also serve as the actuator 305 in FIG. Specifically, a part of the stage (not shown) includes the second measurement window casing 408, and this stage is normal to the moving direction of the measuring window 107 and the moving direction of the measuring window 107. Can move in the direction of the plane containing the direction vector.

FIG. 13 is a further modification of the measurement window 107 described in the present embodiment. In the measurement window portion 107 of FIG. 13, the tilt adjustment plate 1209 described in FIG. 12 is disposed on the second measurement window casing 408. As a result, the measurement window 107 can adjust the inclination of the measurement window 201.

The measurement window 201 of this embodiment is scanned in a one-dimensional direction or a two-dimensional direction with respect to a plane including a vector in the normal direction with respect to the direction in which the propagation distance of the terahertz wave pulse changes. As a result, since the measurement point moves relative to the terahertz wave pulse, a multidimensional tomographic image can be acquired. By realizing the movement of the measurement point of the terahertz wave pulse by the movement of the measurement window 201, the measurement point moving mechanism can be arranged outside the housing 106 of the apparatus. As a result, the volume inside the housing 106 can be reduced, and the time required for adjusting the measurement environment can be shortened. This facilitates downsizing the apparatus and stabilizing the measurement environment.

(Embodiment 4)
Another embodiment in which the idea of the present invention can be implemented will be described with reference to the drawings. Specifically, the mechanism of the measurement window unit 107 described so far is applied to the generation unit 101 and the detection unit 102. In addition, the description of the part which is common in the above description is abbreviate | omitted.

FIG. 5 shows the structure of the measurement window 107 of the present embodiment. The measurement window 509 is a member for condensing the terahertz wave pulse on the element 510. In many cases, a hemispherical lens or a super hemispherical lens is applied. The element 510 is disposed in close contact with the measurement window 509. FIG. 5B shows a configuration example of the element 510. The element 510 is an element in which an antenna electrode 511 and a feeding electrode 512 are formed on a semiconductor substrate 514. This element is also called a photoconductive element. As the semiconductor substrate 514, for example, gallium arsenide (LT-GaAs) or indium gallium arsenide (LT-InGaAs) grown at a low temperature can be used. The material of the semiconductor substrate 514 is not limited to this, and a known material that can generate or detect a terahertz wave can be applied. The shape and size of the antenna electrode 511 and the feeding electrode 512 are appropriately designed according to the wavelength and spectrum shape of the terahertz wave pulse to be used. The hemispherical lens and the super hemispherical lens are preferably made of a material having small loss and dispersion with respect to the terahertz wave. For example, high resistance silicon can be applied. The element is not limited to this as long as the element can generate and detect a terahertz wave.

In FIG. 5, the measurement window 509 is supported by the second measurement window housing 508. The first measurement window housing 507 is supported by the housing 106 by the extendable part 306. Further, the first measurement window casing 507 and the second measurement window casing 508 are arranged in close contact with each other. As described in the third embodiment, the first measurement window casing 507 is a part that moves the measurement window 509 and the element 510 in the direction in which the propagation distance of the terahertz wave pulse changes. The second measurement window casing 508 moves the measurement window 509 and the element 510 in a one-dimensional direction or a two-dimensional direction with respect to a plane including a vector normal to the direction in which the propagation distance of the terahertz wave pulse changes. Part. An actuator 305 is connected to the second measurement window casing 508 as shown in the figure, and a force for moving the first measurement window casing 507 and the second measurement window casing 508 is applied.

With the above configuration, the position of the element 510 can be adjusted via the measurement window 107. Note that the measurement window 509 having the configuration of FIG. 5 is not necessarily required, and the element 510 may also serve as the measurement window 509. According to the configuration of the present embodiment, either or both of the generation unit and the detection unit are arranged on the opposite side of the housing from the propagation path of the electromagnetic wave pulse. In this manner, since at least one of the generation unit 101 and the detection unit 102 can be disposed outside the housing 106, the volume inside the housing 106 can be reduced. As a result, the time required for adjusting the atmosphere inside the housing 106 can be shortened, and the apparatus can be easily downsized.

(Embodiment 5)
Another embodiment in which the idea of the present invention can be implemented will be described with reference to the drawings. Specifically, it is a modification of the apparatus described in the first embodiment, and discloses a form in which this apparatus is formed into a probe. That is, this embodiment is a probe for measuring an object to be measured, and further includes a waveguide section for guiding an electromagnetic wave pulse, and the probe includes the measurement window section at an end thereof. In addition, the description of the part which is common in the above description is abbreviate | omitted.

FIG. 6 shows the configuration of the probed apparatus of this embodiment. FIG. 6 (a) is a diagram showing the configuration of the tip portion of the probe 618. FIG. The distal end portion of the probe 618 includes a measurement window portion 607, a housing 606, and a coating portion 615. The measurement window 607 has the same configuration as that described in the above embodiments. However, the material constituting the measurement window 607 is appropriately selected depending on the use environment of the probe 618. As described above, the position of the measurement window 607 can be adjusted by using the actuator arranged inside the housing 606 or the probe 618 itself as the measurement object 108 as shown in FIGS. 6 (b) and 6 (c). There is a form of pressing. FIG. 6B shows a form in which the focal point of the terahertz wave pulse T ₁ is adjusted to the first interface 618 with respect to the measurement object 108 having the first interface 618 and the second interface 619. In this state, when adjusting the focal position of the terahertz wave pulse T ₁ to the second interface 619, the measurement window 607 is mounted in the process of pressing the probe 618 against the measurement object 108 as shown in FIG. Move inside 606. This is to allow for movement of the focal point of the terahertz wave pulse T _1.

The housing 606 is made of a material having strength that can support the measurement window 607. When the covering portion 615 has sufficient strength and rigidity, the covering portion 615 may also serve as the housing 606.

As shown in FIG. 6, the covering portion 615 includes a waveguide portion 616 that guides the terahertz wave pulse. A known waveguide form can be applied to the waveguide unit 616. For example, a coaxial waveguide or a hollow fiber can be applied. The material constituting the waveguide 616 is preferably a material having as little loss and dispersion as possible with respect to the terahertz wave. FIG. 6 (a) shows an example in which the propagation direction of the terahertz wave pulse is adjusted by the shape of the tip of the waveguide 616. However, the adjustment of the propagation direction of the terahertz wave pulse is not limited to this form, and an optical element (mirror or lens) arranged inside the housing 606 may be used.

According to the apparatus of the present embodiment, since the measurement window 607 is provided at the tip of the probe 618, the focal position of the terahertz wave connected to the surface or inside of the measurement object 108 in contact with the measurement window 607 can be changed. Can be. As a result, since it becomes easy to move the focal position to a position where the measurement object 108 is desired to be measured, the structure of the measurement object 108 can be accurately observed.

One aspect of the present invention is the surface of an object to be measured disposed in a measurement window portion that is movably provided in a casing that adjusts an atmosphere surrounding the propagation path including at least a part of the propagation path of the electromagnetic pulse by an electromagnetic pulse. Or it is also a measurement object information acquisition method which acquires the information of an internal structure. This method has the steps described in the section for solving the above-mentioned problems. According to the present invention, it is possible to provide a program for causing a computer for acquiring information on the measurement object to execute the steps of the above-described measurement object information acquisition method. That is, a storage medium in which a code of a software measurement object information acquisition program that implements each function may be provided to a system or an apparatus. The functions of the above-described embodiments can be realized by the computer (or CPU or MPU) of the system or apparatus reading out and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. As a storage medium for supplying such a program code, for example, a hard disk, an optical disk, a magneto-optical disk, or the like can be used. Alternatively, a CD-ROM, CD-R, magnetic tape, nonvolatile memory card, ROM, or the like can be used. The functions of the above-described embodiments are not only realized by executing the program code read by the computer. This includes the case where the OS (operating system) running on the computer performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized by the processing. ing. Further, the program code read from the storage medium may be written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. Thereafter, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing based on the instruction of the program code, and the functions of the above-described embodiments are realized by the processing. It is a waste.

As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

101 ... Generation unit 102 ... Detection unit 103 ... Light source 104 ... Delay optics unit 105 ... Drive unit 106 ... Case 107 ... Measurement window 108 ... Measurement object 109・ ・ Waveform acquisition unit, 110 ・ ・ Relative position monitoring unit, 111 ・ ・ Propagation distance database, 112 ・ ・ Physical property database, 113 ・ ・ Waveform reconstruction unit, 114 ・ ・ Display unit

Claims (16)

An information acquisition device that acquires a time waveform using time domain spectroscopy and acquires information on a measurement object,
A generator that generates terahertz waves ;
A detection unit for detecting terahertz waves from the measurement object;
A waveform acquisition unit that acquires a time waveform of a terahertz wave using the output of the detection unit;
A housing including a measurement window disposed in the propagation path, including at least a part of the propagation path of the terahertz wave from the generation unit to the detection unit;
A window having transparency to the terahertz wave from the generator, and disposed in the housing;
A moving mechanism for moving a relative position between the window and the parallel propagation region of the terahertz wave from the generation unit so that the propagation distance of the terahertz wave changes ,
The terahertz wave from the generating unit is configured to irradiate the measurement object through the window unit ,
Based on the time waveform acquired by the waveform acquisition unit, acquires information on the measurement object in which a change in the propagation distance of the terahertz wave generated by the reflection unit of the measurement object moving in and out of the parallel propagation region is compensated An information acquisition apparatus characterized by: The time waveform of the terahertz wave from the measurement object is obtained by referring to the output of the detection unit acquired with the relative position moved so that the reflection part of the measurement object is located in the parallel propagation region. get
The information acquisition apparatus according to claim 1. A propagation distance database for storing information on a relationship between a relative position between the parallel propagation region and the window and a propagation distance of the terahertz wave from the generation unit to the detection unit
The information acquisition apparatus according to claim 1, wherein the information acquisition apparatus is an information acquisition apparatus. A relative position monitoring unit that monitors a relative position between the parallel propagation region and the window ;
And Properties database information of the physical properties of the object substance of the distinguished name and the material is stored,
The time waveform acquired by the waveform acquisition unit of the terahertz wave from the window, the change in the propagation distance of the terahertz wave with respect to the relative position acquired from the propagation distance database, and the physical properties stored in the physical property database information and, with further having a waveform reconstruction unit for constructing the reconstruction wave time waveform of the terahertz wave from the measurement object,
The information acquisition apparatus according to claim 3 . A support part for supporting the window part;
A sealing portion disposed between the support portion and the housing.
The information acquisition apparatus according to claim 1, wherein the information acquisition apparatus is an information acquisition apparatus. Before Kifu stop portion, in the plane direction of the surface to place the measurement of the window, according to claim 5, characterized in that it is disposed between the housing and the window Information acquisition device. The sealing portion is in contact with the casing and the window portion.
The information acquisition apparatus according to claim 5, wherein the information acquisition apparatus is an information acquisition apparatus. The information acquisition apparatus according to claim 5 , wherein the support portion moves while being in contact with the sealing portion. Information acquiring apparatus according to any one of claims 1 8, characterized in that it comprises an actuator for moving said window portion in the thickness direction of the measured object. The generating unit and the detection unit, the information acquiring apparatus according to any one of claims 1 to 9, characterized in that it is arranged in the housing. Having an inclination adjusting mechanism for adjusting the inclination of the window portion ;
Information acquiring apparatus according to claim 1, any one of 10, characterized in that. The moving mechanism is
A first stage capable of moving the window so that the propagation distance of the terahertz wave changes;
A second stage disposed on the first stage, movable in an in-plane direction of the object to be measured, and supporting the window portion.
The information acquisition apparatus according to claim 1, wherein the information acquisition apparatus is an information acquisition apparatus. A probe in which the window is disposed at an end;
A waveguide unit disposed in the probe and disposed in at least one of a terahertz wave propagation path from the generation unit to the window unit and a terahertz wave propagation path from the window unit to the detection unit When the information acquisition apparatus according to claim 1, any one of 12, further comprising a. The terahertz wave is a terahertz wave pulse having a component in an arbitrary frequency band within a range of 0.03 THz to 30 THz.
Information acquiring apparatus according to any one of claims 1 to 13, characterized in that. The information acquisition apparatus according to claim 14 , wherein the window is flattened so that the terahertz wave pulse cannot recognize a structure. Flatness of the window portion, the When the center wavelength of the terahertz wave from the generator lambda, according to any one of claims 1 to 15, characterized in that 1 / 20Ramuda less than 1 / 100Ramuda Information acquisition device.

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