JP2011153856A - Device and method for measurement of particle size using terahertz wave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for measurement of a particle size using a terahertz wave, capable of measuring a particle size inexpensively and quickly without requiring much labor. <P>SOLUTION: The device includes: a laser diode 1 for emitting laser light; a beam splitter 2 for splitting laser light emitted from the laser diode 1 into first laser light and second laser light; a terahertz wave oscillating antenna 5 for oscillating a terahertz wave by irradiation with the first laser light; a terahertz wave receiving antenna 8 for detecting a terahertz wave at a detection timing based on the second laser light, and generating a detection signal corresponding to the intensity of the detected terahertz wave; and a data holding part 52 and a data processing part 56 for calculating a characteristic quantity only from signal intensity data based on a detection signal generated by the terahertz wave receiving antenna 8 when a object to be measured 100 is installed in a terahertz wave path, and estimating the particle size of the object to be measured 100 by referring to a database 58 holding data of the particle size corresponding to the characteristic quantity. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a particle size measuring apparatus and a particle size measuring method for measuring the particle size of a measurement object using terahertz waves.

  In recent years, attention has been focused on terahertz waves in the middle region between radio waves and light waves. The use of terahertz waves has been delayed because transmission and reception are difficult. However, the use of terahertz waves has become possible due to recent advances in laser and semiconductor technologies. Although there are differences depending on the academic field, the terahertz wave indicates a region of 30 μm to 3 mm in wavelength and 100 GHz to 10 THz in frequency.

  Patent Document 1 describes a powder physical property measuring apparatus and method using terahertz electromagnetic waves for the purpose of observing the physical state of the powder by electromagnetic spectroscopy. This powder physical property measuring apparatus using terahertz electromagnetic waves includes means for holding powder, irradiation means for irradiating the powder with terahertz electromagnetic waves, and receiving means for receiving the terahertz electromagnetic waves that have passed through the powder and converting them into electrical signals. A means for obtaining a difference in propagation time or amplitude at each position of the powder of the terahertz electromagnetic wave passing through the powder based on the output of the receiving means; and a powder on the display device based on the difference Image processing means for performing image processing for displaying the features of the image processing apparatus.

  This powder physical property measuring device is a device that measures and images the physical properties or physical state of the powder itself, and for example, identifies the type of powder by measuring the transmittance of the terahertz electromagnetic wave, or the terahertz electromagnetic wave The powder filling rate can be estimated by measuring the refractive index.

  Patent Document 2 describes a scatterer detection device using terahertz waves that nondestructively detects spawned products such as powders and bubbles contained in water envelopes, capsules, containers, and the like without opening them. The scattered matter detection device using the terahertz wave includes a terahertz wave generation device that generates a terahertz wave, a terahertz wave irradiation device that irradiates the terahertz wave to the inspection object, and a linear component of the terahertz wave that has passed through the inspection object And a scattering intensity detector for detecting the intensity of the scattering component. Further, the terahertz wave irradiation device includes a lens that converts the generated terahertz wave into parallel light, and a diaphragm that irradiates the target with a cross-sectional shape of the parallel light smaller than that of the object to be inspected. The detection apparatus includes a confocal optical system that shields a terahertz wave that has traveled straight through the inspection object in the middle and condenses the terahertz wave scattered by the inspection object at a predetermined position, and the terahertz wave at the condensing position. And a scattering intensity detector for detecting the intensity of.

  According to the scatterer detection apparatus using the terahertz wave, the straight component of the terahertz wave that has passed through the inspection object can be cut and the intensity of the scatter component can be detected. Thus, the powder can be identified.

JP 2004-61455 A JP 2006-71412 A

  However, when measuring the particle size in a structure using terahertz waves, it is common to use a femtosecond laser because of its wide spectral width and high peak power, but it is expensive. There is a point.

  In addition, the conventional measuring apparatus generally uses the transmittance (= (FFT result of the sample / FFT result of the reference) * 100) when measuring the particle size of the object, but calculates the transmittance. For this purpose, it is necessary to measure the signal intensities of both the reference and the sample, and to calculate them for each frequency after performing Fourier transform, and there is a problem that it takes time for signal processing. In addition, a reference refers to the measurement result performed in the state in which no measurement object is installed.

  FIG. 12 is a flowchart showing the operation of a conventional measuring apparatus. The conventional measuring apparatus first measures a reference time waveform (signal strength with respect to time) (step S1). Next, the conventional measuring apparatus measures a time waveform when a measurement object (sample) is installed (step S2). Here, FIG. 13 is an example of a time waveform diagram of a sample (particle diameter 605 μm) and a reference measured by a conventional measuring apparatus.

  Next, the conventional measuring apparatus performs FFT analysis on the reference and the sample (step S3). Here, FIG. 14 is a diagram showing a result of Fourier transform performed on a sample (particle diameter 605 μm) and a reference time waveform measured by a conventional measuring apparatus.

  Next, the conventional measuring apparatus calculates the transmittance for each frequency (step S4). That is, the conventional measuring apparatus extracts arbitrary intensities of the sample and reference at a predetermined frequency based on the FFT conversion result of FIG. 14, and calculates the transmittance based on the above-described equation. Note that a value stored in advance in a database may be used as the arbitrary intensity with respect to the frequency after the Fourier transform of the reference.

  For example, from the time waveform of the sample after Fourier transform shown in FIG. 14, when the arbitrary intensity for the frequency of 0.183 THz is 127, the arbitrary intensity for the frequency of 0.183 THz of the reference is 259 based on the database. Then, the conventional measuring apparatus can calculate the transmittance as (127/259) * 100 = 49 [%].

  Next, the conventional measuring apparatus collates the calculated transmittance with a database (step S5). FIG. 15 is a diagram showing the transmittance with respect to the particle diameter measured in advance at a frequency of 0.183 THz. FIG. 16 is a table showing a database created based on the result of transmittance with respect to the particle diameter measured in advance at a frequency of 0.183 THz. For example, when the calculated transmittance is 49%, the conventional measuring apparatus can derive that the particle size is 605 [μm] by collating with the database shown in FIG.

  Finally, the conventional measuring device displays the derived particle size (605 [μm]) on the display device and ends the process (step S6).

  As described above, the conventional measuring apparatus needs to perform Fourier transform on the signal intensity of both the reference and the sample, and when measuring the reference every time regardless of the database, every measurement is performed. There is a problem that it is necessary to collect data for both the reference and the sample, which is troublesome.

  The present invention solves the above-described problems of the prior art, and is a low-cost particle size measuring apparatus and particle size measurement using a terahertz wave that can quickly measure the particle size without trouble. It is an object to provide a method.

  In order to solve the above problems, a particle size measuring apparatus using terahertz waves according to the present invention includes a laser diode that emits laser light, and laser light emitted by the laser diode as first laser light and second laser light. And a second laser beam emitted from the light divider. The light divider that divides the terahertz wave by being irradiated with the first laser beam emitted from the light divider, and the second laser beam emitted from the light divider. A terahertz wave detecting unit that detects a terahertz wave oscillated by the terahertz wave oscillating unit at a detection timing based on the terahertz wave, and generates a detection signal corresponding to the intensity of the detected terahertz wave, the terahertz wave oscillating unit, and the terahertz wave A signal based on the detection signal generated by the terahertz wave detection unit when a measurement object is installed in the terahertz waveguide between the detection unit and the detection unit. Calculating a feature from only the intensity data, characterized by comprising a estimation unit for estimating the particle size of the object to be measured by reference to the database that holds the data of the particle size corresponding to the feature quantity.

  In order to solve the above problems, a particle size measurement method using a terahertz wave according to the present invention includes a laser light generation step of emitting laser light from a laser diode, and a laser light emitted by the laser diode as a first laser light. Splitting into a second laser beam, a terahertz wave oscillation step for oscillating a terahertz wave when irradiated with the first laser beam emitted in the light splitting step, and the light splitting step. A terahertz wave detecting step for detecting a terahertz wave oscillated by the terahertz wave oscillating step at a detection timing based on the second laser light and generating a detection signal corresponding to the intensity of the detected terahertz wave; The detection generated by the terahertz wave detection step when a measurement object is placed on A feature amount is calculated only from signal intensity data based on the signal, and an estimation step of estimating the particle size of the measurement object by referring to a database holding data on the particle size corresponding to the feature amount is provided. And

  According to the present invention, it is possible to provide a particle size measuring apparatus and a particle size measuring method using a terahertz wave that can be measured at low cost and can be quickly measured without trouble.

It is a figure which shows the structure of the particle size measuring apparatus using the terahertz wave of the form of Example 1 of this invention. It is a figure which shows the detailed structure of the terahertz wave oscillation antenna in the particle size measuring apparatus using the terahertz wave of the form of Example 1 of this invention. It is a figure which shows the detailed structure of the terahertz wave receiving antenna in the particle size measuring apparatus using the terahertz wave of the form of Example 1 of this invention. It is a flowchart figure which shows operation | movement of the particle size measuring apparatus using the terahertz wave of the form of Example 1 of this invention. It is a graph which shows the feature-value obtained by the particle size measuring apparatus using the terahertz wave of the form of Example 1 of this invention. It is a figure which shows the average value and the transmittance | permeability at the time of changing the particle size of a measuring object in the particle size measuring apparatus using the terahertz wave of the form of Example 1 of this invention. It is a figure which shows the detailed structure of the terahertz wave receiving antenna in the particle size measuring apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows one example of a structure of the particle size measuring apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows one example of a structure of the particle size measuring apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows one example of a structure of the particle size measuring apparatus using the terahertz wave of the form of Example 3 of this invention. It is a figure which shows one example of a structure of the particle size measuring apparatus using the terahertz wave of the form of Example 3 of this invention. It is a flowchart figure which shows operation | movement of the conventional particle size measuring apparatus. It is an example of the time waveform figure of the sample measured with the conventional particle size measuring apparatus, and a reference. It is a figure which shows the Fourier-transform result performed with respect to the time waveform of the sample measured with the conventional particle size measuring apparatus, and a reference. It is a figure which shows the transmittance | permeability with respect to the particle size measured in advance with the frequency of 0.183 THz in the conventional particle size measuring apparatus. It is a table | surface which shows the database produced based on the result of the transmittance | permeability with respect to the particle size measured in advance with the frequency of 0.183 THz in the conventional particle size measuring apparatus.

  Hereinafter, embodiments of a particle size measuring apparatus and a particle size measuring method using a terahertz wave according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a particle size measuring apparatus using a terahertz wave according to a first embodiment of the present invention. With reference to FIG. 1, the structure of the particle size measuring apparatus will be described. The particle size measuring apparatus according to the present embodiment includes a laser diode 1, a beam splitter 2, a mirror 3, a lens 4, a terahertz wave oscillation antenna 5, a parabolic mirrors 6 and 7, a terahertz wave receiving antenna 8, a lens 9, a mirror 10, The time delay mechanism 11, the mirror 12, the signal generator 50, the lock-in amplifier 51, the data holding unit 52, the display device 53, the data processing unit 56, the control unit 57, and the database 58 are configured.

  The laser diode 1, the beam splitter 2, the mirrors 3, 10, 12, lenses 4, 9, the terahertz wave oscillation antenna 5, the terahertz wave receiving antenna 8, the parabolic mirrors 6, 7, the time delay mechanism 11, and will be described later. The measurement object 100 is assumed to be on the same plane.

  The laser diode 1 emits laser light. The intensity of this laser light changes within a few picoseconds. The wavelength of the laser light may be any wavelength that can excite a low-temperature grown gallium arsenide substrate of a terahertz wave oscillation antenna 5 and a terahertz wave receiving antenna 8 described later, and is, for example, about 780 nm to 830 nm. Further, the laser output intensity of the laser diode 1 may be such that it can output about 30 mW on the emitter side and about 10 mW on the detector side.

  The beam splitter 2 corresponds to the light splitting unit of the present invention, and splits the laser light emitted by the laser diode 1 into a first laser light and a second laser light.

  The mirror 3 reflects the first laser light emitted from the beam splitter 2 in a predetermined direction.

  The lens 4 condenses the first laser light reflected by the mirror 3.

  The terahertz wave oscillating antenna 5 corresponds to the terahertz wave oscillating unit of the present invention, and oscillates terahertz waves when the first laser light emitted from the beam splitter 2 is irradiated through the mirror 3 and the lens 4.

  FIG. 2 is a diagram showing a detailed configuration of the terahertz wave oscillating antenna 5 in the particle size measuring apparatus using the terahertz wave of the present embodiment. As shown in FIG. 2, the terahertz wave oscillation antenna 5 has a configuration in which a low-temperature grown gallium arsenide substrate 22 is provided on a silicon lens 25, and a signal generator 50 is connected to the electrode 20 on the low-temperature grown gallium arsenide substrate 22. It is connected. The electrode 20 has a shape such as a dipole or a bow tie, and gold is mainly used as a material. Further, the silicon lens 25 uses a hemispherical lens or a super hemispherical lens. Further, a laser beam 23 indicated by a black circle indicates an irradiation spot of the first laser beam irradiated on the gap 21.

  The signal generator 50 applies a voltage to the terahertz wave oscillation antenna 5 and modulates the terahertz wave at a repetition frequency of 11 kHz, for example.

  The parabolic mirrors 6 and 7 are mirrors for guiding the terahertz wave oscillated by the terahertz wave oscillation antenna 5 to the terahertz wave receiving antenna 8. The parabolic mirrors 6 and 7 may be any one that does not attenuate terahertz waves, and examples thereof include metals (iron, aluminum, and the like). The movable stage may be any stage that steps at 20 μm or less.

  The terahertz wave receiving antenna 8 corresponds to the terahertz wave detecting unit of the present invention, detects the terahertz wave oscillated by the terahertz wave oscillating antenna 5 at the detection timing based on the second laser beam emitted by the beam splitter 2, A detection signal corresponding to the intensity of the detected terahertz wave is generated. The terahertz wave receiving antenna 8 may be any device that can receive terahertz waves, and examples thereof include a silicon bolometer.

  FIG. 3 is a diagram showing a detailed configuration of the terahertz wave receiving antenna 8 in the particle size measuring apparatus using the terahertz wave of the present embodiment. As shown in FIG. 3, the terahertz wave receiving antenna 8 has the same configuration as the terahertz wave oscillating antenna 5, and a low-temperature grown gallium arsenide substrate 22 is provided on the silicon lens 25. However, a lock-in amplifier 51 is connected to the electrode 20 on the low-temperature grown gallium arsenide substrate 22 of the terahertz wave receiving antenna 8 instead of the signal generator 50.

  The mirror 12 reflects the second laser light emitted from the beam splitter 2 in a predetermined direction and guides it into the time delay mechanism 11.

  The time delay mechanism 11 corresponds to the time delay unit of the present invention, and gives a time delay to the second laser light emitted from the beam splitter 2 and incident through the mirror 12. Further, the control unit 57 can control the amount of time delay by moving the mirror inside the time delay mechanism 11. This control unit 57 may be installed integrally with the display device 53. As an example of specifications required for the time delay mechanism 11, the time delay mechanism 11 only needs to have a moving range of the internal mirror of 2 cm to 5 cm. The moving speed may be 20 kpps (Pulse per second) at the maximum and 1 kpps at the minimum. Moreover, the movement pitch should just operate | move every 10 micrometers and movement accuracy should just be 0.015 mm.

  The mirror 10 reflects the second laser light emitted by the time delay mechanism 11 in a predetermined direction.

  The lens 9 condenses the second laser light reflected by the mirror 10. The beam splitter 2, mirrors 3, 10, 12 and lenses 4, 9 are preferably able to withstand the output intensity of the laser beam from the laser diode 1 and do not change the intensity of the laser beam.

The lock-in amplifier 51 amplifies the detection signal generated by the terahertz wave receiving antenna 8 in synchronization with the reference signal of the signal generator 50. The lock-in amplifier 51 only needs to have about 10 ⁸ current amplification. Moreover, the voltage power supply should just be what can apply 50V or less.

  The data holding unit 52 and the data processing unit 56 correspond to the estimation unit of the present invention, and the terahertz wave when the measurement object 100 is installed in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave receiving antenna 8. The feature amount is calculated only from the signal intensity data based on the detection signal generated by the receiving antenna 8, and the particle size of the measurement object 100 is estimated by referring to the database 58 holding the particle size data corresponding to the feature amount. To do.

  Here, the “feature amount” of the present invention refers to an amount that can be calculated only from signal intensity data when the measurement object 100 is placed in a terahertz waveguide. Therefore, the “transmittance” described as the prior art does not correspond to the “feature amount” of the present invention because signal intensity data when the measurement object 100 is not installed in the terahertz waveguide is also required.

  The estimation unit (the data holding unit 52 and the data processing unit 56) calculates an average value, a standard deviation, a maximum value, a peak value, an RMS (Root Mean Square), when calculating the feature amount based on the signal strength data. At least one of a waveform rate, an impact index, a crest rate, a skewness, and a kurtosis is calculated as a feature amount. Details of the feature amount will be described later.

  To describe each configuration, the data holding unit 52 holds signal intensity data based on the detection signal generated by the terahertz wave receiving antenna 8. Further, the data processing unit 56 calculates a feature amount based on the signal intensity data held in the data holding unit 52 and refers to the database 58 via the data holding unit 52 to determine the particle size of the measurement object 100. presume.

  The database 58 holds data on particle diameters corresponding to the feature values examined in advance. The data stored in the database 58 is created by measuring in advance using glass beads having a known particle diameter, for example, and investigating the relationship between the feature value such as the average value and the particle diameter.

  The display device 53 is a device for displaying signal intensity data based on the detection signal output by the lock-in amplifier 51 and the particle size estimated by the estimation unit (the data holding unit 52 and the data processing unit 56).

  Next, the operation of the present embodiment configured as described above will be described. FIG. 4 is a flowchart showing the operation of the particle size measuring apparatus using the terahertz wave of this embodiment. It is assumed that the database 58 already stores data on feature quantities and the corresponding particle sizes.

  First, the particle size measuring apparatus using the terahertz wave of the present embodiment measures the time waveform of the sample as shown in FIG. 13 (step S11). Specifically, the user installs the measuring object 100 in the terahertz waveguide. The measurement object 100 is a granular material or a powder material, and is stored in a case such as polycarbonate.

  The laser diode 1 emits laser light (laser light generation step). The beam splitter 2 splits the laser light emitted from the laser diode 1 into a first laser light and a second laser light (light splitting step). Here, the first laser light is laser light on the emitter side toward the terahertz wave oscillation antenna 2. The second laser light is laser light on the detector side that faces the terahertz wave receiving antenna 8.

  The laser light (first laser light) on the emitter side is collected by the lens 4 and applied to the terahertz wave oscillation antenna 5. The terahertz wave oscillation antenna 5 irradiated with the first laser beam oscillates a terahertz wave when a voltage is applied by the signal generator 50 (terahertz wave oscillation step).

  The oscillated terahertz wave is reflected by the parabolic mirrors 6 and 7 and applied to the terahertz wave receiving antenna 8. On the other hand, the laser beam (second laser beam) on the detector side is applied to the terahertz wave receiving antenna 8 as in the emitter side.

  At this time, the optical components are installed so that the optical distance from the beam splitter 2 through the terahertz wave oscillation antenna 5 to the terahertz wave receiving antenna 8 matches the distance from the beam splitter 2 to the terahertz wave receiving antenna 8.

  Since the terahertz wave oscillated from the terahertz wave oscillation antenna 5 is a pulse and the pulse width is several picoseconds, there is no measuring device that receives one pulse at a time. Therefore, the particle size measuring apparatus according to the present embodiment causes the terahertz wave oscillation antenna 5 to transmit the terahertz pulse repeatedly, generates a time delay by changing the optical distance of the time delay mechanism 11, and sets each location of the terahertz pulse. Terahertz pulses are measured by measuring sequentially.

  The terahertz wave receiving antenna 8 detects a terahertz wave oscillated by the terahertz wave oscillation antenna 5 at a detection timing based on the second laser beam emitted from the beam splitter 2, and a detection signal corresponding to the intensity of the detected terahertz wave (Terahertz wave detection step).

  Specifically, the second laser light is applied to the gap 21 of the terahertz wave receiving antenna 8 to excite electrons, and the terahertz wave is applied thereto, whereby a minute current flows through the electrode 20. The lock-in amplifier 51 synchronizes with the signal generator 50 and detects and amplifies this minute current as a detection signal.

  Next, the particle size measuring apparatus using the terahertz wave of the present embodiment calculates a feature amount (step S12) and collates it with a database (step S13). Specifically, the data holding unit 52 and the data processing unit 56 obtain the feature amount from only the signal intensity data based on the detection signal generated by the terahertz wave receiving antenna 8 when the measurement object 100 is installed in the terahertz waveguide. The particle size of the measuring object 100 is estimated by referring to the database 58 that calculates and holds the data of the particle size corresponding to the feature amount (estimation step).

  Here, an average value, standard deviation, maximum value, peak value, RMS, waveform rate, impact index, crest factor, skewness, and kurtosis will be described as examples of feature amounts.

First, the average value is a value obtained by dividing the sum of absolute values by the data points based on a time waveform in a state where the measuring object 100 is installed between the parabolic mirrors 6 and 7.

The standard deviation is obtained by calculating the following equation (2) based on a time waveform in a state where the measuring object 100 is installed between the parabolic mirrors 6 and 7.

  The maximum value is obtained by taking the maximum absolute value from the time waveform in a state where the measuring object 100 is installed between the parabolic mirrors 6 and 7.

The peak value is an average value from the time waveform in the state in which the measuring object 100 is installed between the parabolic mirrors 6 and 7 to the tenth in descending order of the absolute value.

RMS is calculated from the following equation (4) from a time waveform in a state where the measuring object 100 is installed between the parabolic mirrors 6 and 7.

The skewness is obtained by calculating the following equation (5) from a time waveform in a state where the measuring object 100 is installed between the parabolic mirrors 6 and 7.

The degree of kurtosis is obtained by calculating the following equation (5) from a time waveform in a state where the measuring object 100 is installed between the parabolic mirrors 6 and 7.

  Furthermore, not only the feature quantity of the dimensional parameter but also the waveform ratio, the impact index, and the crest factor, which are the feature quantities of the dimensionless parameter, can be obtained using the values obtained by the above-described formula. Here, the waveform rate = standard deviation / average value. Also, impact index = peak value / standard deviation. Furthermore, crest factor = peak value / average value.

  On the other hand, as described above, the user previously measures the relationship between the particle size and each feature amount, and creates the database 58. When the measurement of the sample (measurement object 100) is completed, the data processing unit 56 calculates the above-described feature amount from the signal intensity data held in the data holding unit 52, and compares the calculated feature amount with the database 58. To estimate the particle size.

  Finally, the display device 53 displays the particle size estimated by the estimation unit (the data holding unit 52 and the data processing unit 56) on a display or the like (step S14).

  As described above, according to the particle size measuring apparatus and the particle size measuring method using the terahertz wave according to the form of the first embodiment of the present invention, the particle size is measured quickly and without cost. be able to.

  That is, since the particle size measuring apparatus and the particle size measuring method of the present embodiment use the laser diode 1 instead of using the conventional high-cost femtosecond laser, the apparatus can be kept at low cost. Has the advantage.

  Here, FIG. 5 is a graph showing the characteristic amount obtained by the particle size measuring apparatus using the terahertz wave of the present embodiment, and the horizontal axis is the particle size. As shown in FIG. 5, the feature quantities of any dimensional parameters tend to decrease as the particle size of the measurement object 100 increases, and it can be said that the particle size can be determined. That is, the experimental results of FIG. 5 show that even if the laser diode 1 is used instead of the high-cost femtosecond laser as in the particle size measuring apparatus of the present embodiment, there is a significant difference in the feature amount, so It shows that the measurement is sufficiently possible.

  In addition, since the conventional measuring apparatus uses the transmittance when measuring the particle size of an object, it measures the signal intensity of both the reference and the sample with no object to be measured, both of which are Fourier transforms. There is a problem in that it is necessary to calculate for each frequency after the conversion, and it takes time to process the signal. On the other hand, the particle size measuring apparatus of the present embodiment calculates the feature amount only from the signal intensity data based on the detection signal generated by the terahertz wave receiving antenna 8 when the measurement object 100 is installed in the terahertz waveguide. Since the particle size is estimated based on the calculated feature amount, it is not necessary to measure the reference in a state where no measurement object is installed as in the conventional case, and further, it is not necessary to perform Fourier transform, so that signal processing is performed. There is an advantage that it can be simplified.

  FIG. 6 is a diagram showing an average value and transmittance when the particle diameter of the measurement object 100 is changed in the particle diameter measuring apparatus using the terahertz wave of the present embodiment. As shown in FIG. 6, both the transmittance and the average value tend to decrease as the particle size of the measuring object 100 increases. That is, the experimental results shown in FIG. 6 show that even when the average value is adopted as the feature quantity instead of the transmittance as in the particle size measuring device of the present embodiment, the particle size is equivalent to that of the conventional device using the transmittance. It shows that the diameter can be measured. Therefore, the particle size measuring apparatus and the particle size measuring method using the terahertz wave of the present embodiment can measure at the same level as the conventional apparatus, but can simplify the signal processing, and can be performed quickly without much trouble. The particle size can be measured.

  Next, the configuration of the particle size measuring apparatus using the terahertz wave according to the second embodiment of the present invention will be described. The particle size measurement apparatus of the present embodiment is different from that of the first embodiment in that it includes at least one of an analog filter 55, a digital filter 54, and an optical filter 13. Specifically, the terahertz wave receiving antenna 8 includes at least one of an analog filter 55 and a digital filter 54. When the optical filter 13 is provided, the particle size measuring apparatus according to the present embodiment passes only the terahertz wave in a predetermined frequency band in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave receiving antenna 8. An optical filter 13 is provided.

  FIG. 7 is a diagram showing a detailed configuration of the terahertz wave receiving antenna 8a in the particle size measuring apparatus using the terahertz wave of the present embodiment when the analog filter 55 is provided. The difference from the terahertz wave receiving antenna 8 of the first embodiment is that an analog filter 55 is connected to the electrode 20.

  FIG. 8 is a diagram illustrating a configuration of a particle size measuring apparatus using a terahertz wave according to the present embodiment when the digital filter 54 is provided. The difference from the particle size measuring apparatus of the first embodiment is that a digital filter 54 is provided between the terahertz wave receiving antenna 8 and the lock-in amplifier 51.

  FIG. 9 is a diagram illustrating a configuration of a particle size measuring apparatus using a terahertz wave according to the present embodiment when the optical filter 13 is provided. The difference from the particle size measuring apparatus of Example 1 is that an optical filter 13 is provided in the terahertz waveguide. The installation location of the optical filter 13 may be anywhere in the terahertz waveguide from the terahertz wave oscillation antenna 5 to the terahertz wave receiving antenna 8, and does not matter before and after the measurement object 100.

  In the present embodiment, the optical filter 13, the analog filter 55, and the digital filter 54 are all filters through which 0.25 THz or less passes.

  Other configurations are the same as those of the first embodiment, and redundant description is omitted.

  Next, the operation of the present embodiment configured as described above will be described. Basically, the operation is the same as that of the particle size measuring apparatus of the first embodiment. However, when the terahertz wave receiving antenna 8 includes at least one of the analog filter 55 and the digital filter 54, the terahertz wave receiving antenna 8 serves as a noise filter with respect to the generated detection signal, and thus is input to the lock-in amplifier. The detection signal is a signal from which noise components are removed. Further, when the optical filter 13 is provided, the terahertz wave receiving antenna 8 can receive the terahertz wave from which the noise component has been removed because it plays the role of a noise filter with respect to the terahertz wave.

  Other operations are the same as those in the first embodiment, and redundant description is omitted.

  As described above, according to the particle size measuring apparatus according to the second embodiment of the present invention, not only can the same effect as the first embodiment be obtained, but also the terahertz wave or the noise component of the detection signal can be removed. As a result, the difference in the feature amount according to the particle diameter is clearly shown, so that the particle diameter can be determined more easily and accurately. In addition, when setting it as the structure which added the filter like a present Example, the user needs to produce the database in case a filter exists beforehand.

  FIG. 10 is a diagram illustrating a configuration of a particle size measuring apparatus using terahertz waves according to the third embodiment of the present invention. The difference from the configuration of the first embodiment is that the data processing unit 56, the time delay mechanism 11 and the control unit 57 are not provided.

  Other configurations are the same as those of the first embodiment, and redundant description is omitted.

  Next, the operation of the present embodiment configured as described above will be described. Basically, the operation is the same as that of the particle size measuring apparatus of the first embodiment. However, since the time delay mechanism 11 is not installed, the particle size measuring apparatus of the present embodiment cannot give a time delay to the second laser beam and cannot obtain a time waveform. Therefore, the detection signal from the terahertz wave receiving antenna 8 indicates the intensity at one point of the terahertz wave.

  The data holding unit 52 corresponds to the estimation unit of the present invention, and is generated by the terahertz wave receiving antenna 8 when the measurement object 100 is installed in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave receiving antenna 8. The feature amount is calculated only from the signal intensity data based on the detected signal, and the particle size of the measuring object 100 is estimated by referring to the database 58 holding the particle size data corresponding to the feature amount.

  Here, the data holding unit 52 uses the signal strength data as it is as the feature amount. That is, the particle size measuring apparatus according to the present embodiment does not calculate the feature amount through the calculation process such as the average value, and thus the data processing unit 56 is unnecessary.

  Note that the database 58 holds data on the particle diameter corresponding to the signal intensity examined in advance. The data stored in the database 58 is created by, for example, measuring in advance using glass beads having a known particle diameter and investigating the relationship between the signal intensity and the particle diameter.

  As described above, according to the particle size measuring apparatus according to the third embodiment of the present invention, not only the same effects as those of the first embodiment can be obtained, but also the data processing unit 56, the time delay mechanism 11, and the control unit. Since 57 is unnecessary, cost reduction can be realized. That is, it can be said that the time delay mechanism 11 is not necessarily an essential component for realizing the present invention.

  Moreover, FIG. 11 is a figure which shows another structural example of the particle size measuring apparatus using the terahertz wave of Example 3 of this invention, and the optical filter 13 is further provided. By adopting such a configuration, the particle diameter can be determined more easily and accurately as in the second embodiment. Further, as described in the second embodiment, the analog filter 55 or the digital filter 54 can be provided, and the same effect as that of the second embodiment can be obtained.

  The particle size measuring device according to the present invention can be used in a particle size measuring device and a particle size measuring method for measuring the particle size of a measurement object using terahertz waves.

DESCRIPTION OF SYMBOLS 1 Laser diode 2 Beam splitter 3 Mirror 4 Lens 5 Terahertz wave oscillation antennas 6 and 7 Parabolic mirror 8, 8a Terahertz wave receiving antenna 9 Lens 10 Mirror 11 Time delay mechanism 12 Mirror 13 Optical filter 20 Electrode 21 Gap 22 Low temperature growth gallium Arsenic substrate 23 Laser beam 25 Silicon lens 50 Signal generator 51 Lock-in amplifier 52 Data holding unit 53 Display device 54 Digital filter 55 Analog filter 56 Data processing unit 57 Control unit 58 Database 100 Measurement object

Claims (6)

A laser diode that emits laser light;
A light splitting section for splitting the laser light emitted by the laser diode into a first laser light and a second laser light;
A terahertz wave oscillating unit that oscillates a terahertz wave by being irradiated with the first laser light emitted by the light splitting unit;
Terahertz wave detection for detecting a terahertz wave oscillated by the terahertz wave oscillating unit at a detection timing based on the second laser light emitted by the light splitting unit and generating a detection signal corresponding to the intensity of the detected terahertz wave And
The feature amount is calculated only from the signal intensity data based on the detection signal generated by the terahertz wave detection unit when a measurement object is installed in the terahertz waveguide between the terahertz wave oscillation unit and the terahertz wave detection unit. An estimation unit that estimates the particle size of the measurement object by referring to a database that holds data on the particle size corresponding to the feature amount;
A particle size measuring apparatus using a terahertz wave.   The particle size measuring apparatus using a terahertz wave according to claim 1, further comprising a time delay unit that gives a time delay to the second laser light emitted by the light splitting unit.   The estimation unit calculates an average value, standard deviation, maximum value, peak value, RMS, waveform rate, impact index, crest factor, skewness, and kurtosis when calculating a feature value based on the signal strength data. 3. The particle size measuring apparatus using terahertz waves according to claim 2, wherein at least one is calculated as a feature amount.   The optical filter which passes only the terahertz wave of a predetermined | prescribed frequency band in the terahertz waveguide between the said terahertz wave oscillation part and the said terahertz wave detection part is provided, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. A particle size measuring apparatus using the terahertz wave described in the item.   The particle size measuring apparatus using terahertz waves according to any one of claims 1 to 4, wherein the terahertz wave detection unit includes at least one of an analog filter and a digital filter. A laser beam generation step of emitting laser beam from the laser diode;
A light splitting step for splitting the laser beam emitted by the laser diode into a first laser beam and a second laser beam;
A terahertz wave oscillating step of oscillating a terahertz wave by being irradiated with the first laser light emitted by the light splitting step;
Terahertz wave detection for detecting the terahertz wave oscillated by the terahertz wave oscillating step at a detection timing based on the second laser light emitted by the light splitting step and generating a detection signal corresponding to the intensity of the detected terahertz wave Steps,
A database that calculates feature amounts only from signal intensity data based on the detection signal generated by the terahertz wave detection step when a measurement object is placed in the terahertz waveguide, and holds data of particle sizes corresponding to the feature amounts An estimation step of estimating the particle size of the measurement object by referring to
A particle size measuring method using a terahertz wave.

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