JP5710355B2 - Inspection apparatus and inspection method using terahertz waves - Google Patents

Description

  The present invention relates to an inspection apparatus and an inspection method for inspecting physical quantities and physical properties of an inspection object using a terahertz wave.

  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.

  An apparatus for inspecting a physical quantity or physical property of an inspection object by using the terahertz wave has been disclosed. For example, there is a particle diameter measuring apparatus for measuring the particle diameter of the object. Such a conventional particle size measuring apparatus generally uses a transmittance (= (FFT result of a sample / FFT result of a reference) * 100) when measuring the particle size of an object. Therefore, it is necessary to measure the signal intensities of both the reference and the sample and calculate them for each frequency after performing Fourier transform, and there is a problem in that it takes time to process the signal. In addition, a reference refers to the measurement result performed in the state in which no measurement object is installed.

  FIG. 18 is a flowchart showing the operation of the conventional particle size 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. 19 is an example of a time waveform diagram of a sample (particle diameter 110 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). Next, the conventional measuring apparatus calculates the transmittance for each frequency (step S4). That is, the conventional measuring apparatus extracts the arbitrary intensity of the sample and reference at a predetermined frequency based on the FFT conversion result, 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, if the arbitrary intensity for the 0.183 THz frequency is 127 from the time waveform of the sample after Fourier transform, and the arbitrary intensity for the 0.183 THz frequency of the reference is 259 based on the database, The 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). The database stores the transmittance with respect to the particle diameter measured in advance at a predetermined frequency, and the conventional measuring apparatus can derive the particle diameter by comparing the transmittance calculated in step S4 with the database. . Finally, the conventional measuring device displays the derived particle size on the display device and ends the process (step S6).

JP 2004-61455 A JP 2006-71412 A

  However, the conventional measuring apparatus needs to perform Fourier transform on the signal intensity of both the reference and the sample. Further, when the reference is measured every time regardless of the database, the reference and the sample are measured each time the measurement is performed. There is a problem in that it is necessary to collect data for both, and it takes time and effort.

  In particular, a conventional measuring apparatus amplifies a terahertz wave received by an antenna using a lock-in amplifier when taking data, but a more accurate value is measured when the time constant of the lock-in amplifier is set to 1 s. Therefore, it is necessary to wait for a time three times the time constant (= 3 s) to measure one point. If 1024 points are measured as appropriate values for performing the Fourier transform, the conventional measuring apparatus takes 3 × 1024 = 3072 s (about 50 minutes), and the measurement of the terahertz time waveform is very time consuming. . Further, the setting of the time constant of the lock-in amplifier can be changed. However, if the time constant is changed as short as about 100 ms, for example, there is a problem that the capacity is not sufficient and an accurate intensity cannot be measured.

  The present invention solves the above-described problems of the prior art, and an object thereof is to provide an inspection apparatus and an inspection method using a terahertz wave that can be measured in a short time without causing a decrease in measurement accuracy. .

In order to solve the above problems, an inspection apparatus using a terahertz wave according to the present invention is generated by a light splitting unit that splits a laser beam into a first laser beam and a second laser beam, and the light splitting unit. A terahertz wave oscillating unit that oscillates a terahertz wave when irradiated with the first laser beam, a time delay unit that gives a time delay to the second laser beam emitted by the light splitting unit, and a time delay by the time delay unit A terahertz wave detecting unit that detects a terahertz wave oscillated by the terahertz wave oscillating unit at a detection timing based on the second laser beam given, and generates a detection signal according to the intensity of the detected terahertz wave; When a measurement object is installed in the terahertz waveguide between the terahertz wave oscillation unit and the terahertz wave detection unit, and the time delay given by the time delay unit is changed The time-series signal intensity data based on the detection signal generated by the terahertz wave detection unit predicts the position where the peak value is shown, and the time delay range given by the time delay unit based on the predicted position is limited to a predetermined range. A signal intensity based on a detection signal generated by the terahertz wave detection unit when a measurement object is installed in a terahertz waveguide between the control unit that controls the range and the terahertz wave oscillation unit and the terahertz wave detection unit An inspection unit that inspects characteristics of the measurement object based on a peak value of data, and a lock-in amplifier that amplifies a detection signal generated by the terahertz wave detection unit, and the control unit includes: The time series signal intensity data has a peak value based on the detection signal generated by the terahertz wave detection unit when the time constant has the first predetermined value. Predicting a position to be indicated, and the inspection unit controls a time delay range provided by the time delay unit based on a position predicted by the control unit to a predetermined limited range and sets a time constant of the lock-in amplifier. Inspecting the characteristics of the measurement object based on the peak value of the signal intensity data based on the detection signal generated by the terahertz wave detection unit when the second predetermined value is larger than the first predetermined value. Features.

It is a figure which shows the structure of the test | inspection 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 test | inspection 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 test | inspection apparatus using the terahertz wave of the form of Example 1 of this invention. It is a time waveform figure at the time of changing the time constant of a lock-in amplifier in the test | inspection apparatus using the terahertz wave of the form of Example 1 of this invention. It is a figure which shows the structure of the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a time waveform figure of the terahertz wave based on each of a plurality of optical paths which have different optical path lengths in the inspection device using the terahertz wave of the form of Example 2 of the present invention. It is a time waveform figure of the detection signal generated by the terahertz wave receiving antenna in the inspection apparatus using the terahertz wave according to the second embodiment of the present invention. It is a figure which shows another structural example of the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows the reflectance in each layer of the multiple reflection mirror in the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows another structural example of the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows the structural example of the fixed delay reflective mirror in the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows another structural example of the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows the structural example of the fixed delay reflective mirror in the test | inspection apparatus using the terahertz wave of the form of Example 2 of this invention. It is a figure which shows the structure of the test | inspection apparatus using the terahertz wave of the form of Example 3 of this invention. It is a figure which shows the structure of the continuous delay reflective mirror in the test | inspection apparatus using the terahertz wave of the form of Example 3 of this invention. It is a figure which shows another structural example of the test | inspection apparatus using the terahertz wave of the form of Example 3 of this invention. It is a figure which shows the structure of the fixed delay transmission plate in the test | inspection 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.

  Hereinafter, embodiments of an inspection apparatus and an inspection 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 an inspection apparatus using a terahertz wave according to a first embodiment of the present invention. The configuration of the inspection apparatus will be described with reference to FIG. The inspection apparatus according to this 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, and a time delay. The mechanism 11 includes a mirror 12, a signal generator 50, a lock-in amplifier 51, a data holding unit 52, a display device 53, a data processing unit 56, a control unit 57, and a database 58.

  Laser diode 1, beam splitter 2, mirrors 3, 10, 12, lenses 4, 9, terahertz wave oscillation antenna 5, terahertz wave receiving antenna 8, parabolic mirrors 6, 7, 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. However, a femtosecond pulse laser may be used instead of the laser diode 1. 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 beam 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 with a repetition frequency of, for example, 11 kHz and ± 10 V.

  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 mirror 12 reflects the second laser light emitted by 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. 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, the mirrors 3, 10, and the lenses 4 and 9 are preferably capable of withstanding the output intensity of the laser beam from the laser diode 1 and do not change the intensity of the laser beam.

  The terahertz wave receiving antenna 8 corresponds to the terahertz wave detection unit of the present invention, and the terahertz wave oscillated by the terahertz wave oscillation antenna 5 at the detection timing based on the second laser beam given the time delay by the time delay mechanism 11. And a detection signal corresponding to the detected intensity of the 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 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 inspection 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. Based on the peak value of the signal intensity data based on the detection signal generated by the receiving antenna 8, the feature of the measurement object 100 is inspected. For example, the inspection unit estimates the particle size of the measurement object 100 by referring to the database 58 that holds the data of the particle size corresponding to the peak value of the signal intensity data.

  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 refers to the database 58 via the data holding unit 52 in order to inspect the characteristics of the measurement object 100 based on the peak value indicated by the signal intensity data held in the data holding unit 52. Thus, the physical quantity (for example, particle size), physical properties, etc. of the measurement object 100 are estimated.

  The database 58 holds data such as physical quantities (for example, particle diameter) and physical properties corresponding to the peak 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 examining the relationship between the peak intensity 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 results of inspection by the inspection unit (the data holding unit 52 and the data processing unit 56).

  Further, the control unit 57 can control the amount of time delay by moving the mirror inside the time delay mechanism 11. Here, the control unit 57 installs the measurement object 100 in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave receiving antenna 8 and changes the time delay given by the time delay mechanism 11. The position where the time-series signal intensity data based on the detection signal generated by the terahertz wave receiving antenna 8 shows the peak value is predicted. Further, the control unit 57 controls the time delay range provided by the time delay mechanism 11 to a predetermined limited range based on the predicted position. This control unit 57 may be installed integrally with the display device 53.

  Next, the operation of the present embodiment configured as described above will be described. Here, it is assumed that the inspection apparatus of this embodiment measures the particle size of the measurement object 100. It is assumed that the data of the peak intensity and the particle size corresponding to the peak intensity are already stored in the database 58.

  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. 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. 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.

  The terahertz wave oscillated from the terahertz wave oscillation antenna 5 is a pulse, and the pulse width is several picoseconds. Therefore, one pulse cannot be received at a time. Therefore, the inspection apparatus of the present embodiment repeatedly transmits the terahertz wave to the terahertz wave oscillation antenna 5, generates a time delay by changing the optical distance of the time delay mechanism 11, and sequentially measures each location of the terahertz wave. To measure the terahertz wave.

  That is, the time delay mechanism 11 gives a time delay to the second laser light emitted from the beam splitter 2 and incident through the mirror 12 (time delay step).

  The terahertz wave receiving antenna 8 detects the terahertz wave oscillated by the terahertz wave oscillating antenna 5 at the detection timing based on the second laser light given the time delay by the time delay mechanism 11 and sets the intensity of the detected terahertz wave. A corresponding detection signal is generated (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.

  On the other hand, the control unit 57 installs the measurement object 100 in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave receiving antenna 8 and changes the time delay given by the time delay mechanism 11. The position where the time-series signal intensity data based on the detection signal generated by the wave receiving antenna 8 shows a peak value is predicted. Further, the control unit 57 controls the time delay range provided by the time delay mechanism 11 to a predetermined limited range based on the predicted position (control step).

  Here, the time waveform (reference) and paraboloid in a state where nothing is left between the paraboloidal mirrors 6 and 7 without using a laser diode without controlling the time delay range to a predetermined limited range. The measurement result in the state where the particles (center particle diameter 110 μm) are set as the measurement object 100 between the mirrors 6 and 7 is as shown in FIG. The beads are glass beads and the case is polycarbonate.

  However, as described above, the control unit 57 of the present embodiment controls the time delay range to a predetermined limited range. Specifically, the inspection apparatus of the present embodiment shortens the time constant of the lock-in amplifier 51 (for example, 100 ms) in order to shorten the measurement time, measures the terahertz waveform by shortening the measurement time, and detects the terahertz peak. Measure the position once and find out the peak position. Since the peak position found out here is a rough position, it can be said that the peak position is a predicted position when measured with an original time constant (for example, 1 s).

  That is, the control unit 57 controls the time constant of the lock-in amplifier 51, and the detection signal generated by the terahertz wave receiving antenna 8 when the time constant of the lock-in amplifier 51 has the first predetermined value (here, 100 ms). Based on the above, the position where the time-series signal strength data shows the peak value is predicted.

  Next, the control unit 57 controls the time delay range provided by the time delay mechanism 11 to a predetermined limited range based on the predicted position. That is, the control unit 57 returns the time constant to an appropriate value (here, 1 s) and measures the intensity peak value again within a predetermined time delay range.

  Normally, this type of terahertz wave transmission / reception apparatus sets the time constant of the lock-in amplifier 51 to 1 s and waits for 3 s, which is three times as long, before measuring. If 1024 points are measured for Fourier transform, the measurement takes 1024 × 3 = 3072 s (about 50 minutes).

    However, since the inspection apparatus of the present embodiment sets and measures the time constant of the lock-in amplifier 51 to the first predetermined value (100 ms in this case), it is 1024 × 0.3 = 307.2 s (about 5 minutes). Measure time series data and identify the peak intensity. Further, the control unit 57 in the inspection apparatus of the present embodiment returns the time constant of the lock-in amplifier 51 to the second predetermined value (here, 1 s), and the time delay range provided by the time delay mechanism 11 is limited to a predetermined value. Control within the range and measure near the peak intensity. Here, for example, if 10 points near the peak intensity are measured, the time required for the measurement is 10 × 3 = 30 s (0.5 minutes). That is, the total measurement time is 5.5 minutes, and the inspection apparatus of the present embodiment can be shortened to 1/10 compared with the measurement time of the conventional apparatus.

  FIG. 4 is a time waveform diagram when the time constant of the lock-in amplifier 51 is changed in the inspection apparatus using the terahertz wave of this embodiment. As shown in FIG. 4, since the difference in peak position between the case where the time constant is set to 1 s and the case where the time constant is set to 100 ms is 1 to 2 points, the inspection apparatus of the present embodiment is, for example, near the detected peak intensity May be measured at five points with a time constant of 1 s.

  Next, the inspection apparatus using the terahertz wave according to the present embodiment calculates the peak intensity of the detection signal by the lock-in amplifier 51 and compares it with the database. Specifically, the inspection unit (the data holding unit 52 and the data processing unit 56) includes 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. Based on the peak value of the signal intensity data based on the detection signal generated by the receiving antenna 8, the characteristic of the measurement object 100 is inspected (inspection step).

  The inspection unit (data holding unit 52 and data processing unit 56) in the present embodiment controls the time delay range provided by the time delay mechanism 11 to a predetermined limited range based on the position predicted by the control unit 57. The signal intensity based on the detection signal generated by the terahertz wave receiving antenna 8 when the time constant of the lock-in amplifier 51 is changed to a second predetermined value (here, 1 s) larger than the first predetermined value (here, 100 ms). Based on the peak value of the data, the characteristics of the measurement object 100 are inspected.

  On the other hand, as described above, the user previously measures the relationship between the particle size and the peak value, 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 peak value from the signal intensity data held in the data holding unit 52, and compares the calculated peak value with the database 58. To estimate the particle size.

  Finally, the display device 53 displays the physical quantity, physical properties, etc. (particle size in the present embodiment) of the measurement object 100 found by the inspection unit (data holding unit 52 and data processing unit 56) on the display or the like. indicate.

  As described above, according to the inspection apparatus and the inspection method using the terahertz wave according to the form of the first embodiment of the present invention, measurement can be performed in a short time without causing a decrease in measurement accuracy.

  That is, the inspection apparatus and inspection method of this embodiment simply inspects the physical quantity and physical properties of the sample based on the peak intensity, so that it is not necessary to perform Fourier transform as in the conventional apparatus, and the position indicating the peak intensity can be quickly displayed. Therefore, the time constant is set to 100 ms and the vicinity of the approximate peak intensity is identified (peak position prediction by the control unit 57), and then the time delay range by the time delay mechanism 11 is limited to the predicted peak position. In addition, since the accurate peak intensity is measured by returning the time constant to 1 s, the measurement can be performed in a short time without causing a decrease in measurement accuracy.

  As a modification, the control unit 57 may predict the peak position by using the measurement result of the reference (measurement performed without installing any measurement object). That is, the control unit 57 measures the measurement object in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave reception antenna 8 based on the position where the time series signal intensity data of the reference measured in advance shows the peak value. 100 is installed, and the position where the time-series signal intensity data based on the detection signal generated by the terahertz wave receiving antenna 8 when the time delay given by the time delay mechanism 11 is changed is predicted.

  Specifically, when the measurement object 100 is installed in the terahertz waveguide, the propagation of the terahertz wave is delayed as compared with the case where nothing is installed. Does not measure the peak intensity of the sample before the reference in time series. Therefore, the control unit 57 predicts that the position at which the sample time-series signal strength data indicates the peak value is later than the position at which the reference time-series signal intensity data indicates the peak value, and based on the predicted position. The range of the time delay given by the time delay mechanism 11 is controlled to a predetermined limited range. The inspection unit may estimate the physical quantity, physical properties, and the like of the measurement object 100 by comparing the reference intensity peak and the sample intensity peak value.

  When the thickness or refractive index of the sample case into which the measurement object 100 is put is known, the control unit 57 may predict the peak position using such information. That is, the control unit 57 places the measurement object 100 in the terahertz waveguide between the terahertz wave oscillation antenna 5 and the terahertz wave reception antenna 8 based on the refractive index and thickness of the sample case into which the measurement object 100 is put. The position where the time-series signal intensity data based on the detection signal generated by the terahertz wave receiving antenna 8 is installed and the time delay given by the time delay mechanism 11 is changed is predicted.

  The electromagnetic wave traveling in the substance is expressed by the relation V = C / n, where the speed of the electromagnetic wave in the substance is V (m / s), the speed of light is C (m / s), and the refractive index of the substance is n. Be late. For example, when the refractive index n of polycarbonate is 1.59 and the thickness is 1 mm, the speed of the electromagnetic wave in the substance is about 1.9 × 10 ^ 8 m / s, and it takes 5.3 ps to advance the thickness of 1 mm. Therefore, the peak position can be expected to be after 10.6 ps, which is the thickness of two sample cases compared to the reference. In terms of distance, since 3 × 10 ^ 8 × 10.6 ps = 3.18 mm, the control unit 57 shifts the time delay mechanism 11 by 1.59 mm, and measures time-series data.

  Note that the thickness depending on the particle size of the measurement object 100 in the sample case has no effect on the peak position because only the amount of transmission of the terahertz wave is attenuated, and the controller 57 predicts the peak position. There is no need to take it into account.

  Next, the configuration of the inspection apparatus using the terahertz wave according to the second embodiment of the present invention will be described. FIG. 5 is a diagram illustrating a configuration of an inspection apparatus using a terahertz wave according to the second embodiment of the present invention. The difference from the inspection apparatus of the first embodiment shown in FIG. 1 is that an optical path adjustment unit 60 is provided between the beam splitter 2 and the terahertz wave receiving antenna 8. The optical path adjusting unit 60 of the present invention has a plurality of optical paths having different optical path lengths on at least one of the first laser light and the second laser light. It is on the optical path.

  Specifically, the optical path adjustment unit 60 has five optical paths with different optical path lengths of 0.87 mm from the optical path 1 to the optical path 5, and the optical path length of the optical path 1 is the shortest and the optical path 5 is the longest. Have a length. Furthermore, the laser intensity of one optical path is adjusted to be about 5 mW.

  The optical path adjustment unit 60 determines the optical path length difference of each optical path based on the frequency showing the strongest intensity when Fourier transform is performed on the signal intensity data of the reference measured in advance. Thereby, the optical path adjustment unit 60 functions like a filter, and acts so that a terahertz wave having a specific frequency is detected by the terahertz wave receiving antenna 8.

  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. FIG. 6 is a time waveform diagram of a terahertz wave based on each of a plurality of optical paths having different optical path lengths in the inspection apparatus using the terahertz wave of the present embodiment. Since the optical path adjustment unit 60 divides the second laser light into five optical paths, the terahertz waves based on the respective optical paths each have an intensity of 1/5 of the original terahertz waveform.

  FIG. 7 is a time waveform diagram of a detection signal generated by the terahertz wave receiving antenna 8 in the inspection apparatus using the terahertz wave according to the present embodiment. In other words, the sum of the terahertz waveforms based on the optical paths 1 to 5 shown in FIG. It is. That is, the terahertz wave receiving antenna 8 detects the terahertz wave oscillated by the terahertz wave oscillating antenna 5 at the detection timing based on the second laser light that has passed through each of the optical paths 1 to 5, and is shown in FIG. Five points will be measured simultaneously.

  Therefore, the inspection apparatus of the present embodiment only needs to measure for one period as shown in FIG. 7, and the range of the time delay provided by the time delay mechanism 11 can be limited to a predetermined range. In other words, the control unit 57 can predict that the peak position is within one cycle, and controls the time delay range provided by the time delay mechanism 11 to a predetermined limited range based on the predicted position. I can say that.

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

  As described above, according to the inspection apparatus according to the second embodiment of the present invention, by providing the optical path adjustment unit 60, five points can be measured simultaneously as shown in FIG. Since the control range can be limited, the physical quantity and physical properties of the measuring object 100 can be estimated by measuring in a short time as in the first embodiment.

As a modification, it is also conceivable to use a multilayer mirror instead of the optical path adjustment unit 60. FIG. 8 is a diagram illustrating another configuration example of the inspection apparatus using the terahertz wave according to the second embodiment of the present invention. In the inspection apparatus shown in FIG. 8, a multilayer mirror 13 is installed between the beam splitter 2 and the terahertz wave receiving antenna 8 instead of the optical path adjustment unit 60.

In other words, the multilayer mirror 13 corresponds to the optical path adjusting unit of the present invention, and has a plurality of optical paths having different optical path lengths on the optical path of the second laser light. Here, FIG. 9 is a diagram showing the reflectance in each layer of the multilayer mirror 13 in the inspection apparatus shown in FIG. Since the second laser light attenuates as it passes through each layer of the multilayer mirror 13, the laser light intensity in each optical path is appropriately controlled by adjusting the reflectance of each layer. For example, the laser irradiation intensity to the multilayer mirror 13 is 55 mW, the first layer reflectance: 10%, the second layer reflectance: 15%, the third layer reflectance: 20%, and the fourth layer reflectance. If the reflectance of the fifth layer is 60%, the reflected laser intensity is 5.5 mW, 6, 7 mW, 6.4 mW, 6.2 mW, and 6.1 mW, respectively.

Since the boundary having five different reflectivities is provided in the multilayer mirror 13, the operation similar to that of the optical path adjustment unit 60 is performed. Therefore, the inspection apparatus shown in FIG. 8 is similar to the inspection apparatus shown in FIG. Five points can be measured at the same time, and the physical quantity and physical properties of the measurement object 100 can be estimated with a short measurement.

  Furthermore, as another modification, it is conceivable to use a fixed delay reflection mirror instead of the optical path adjustment unit 60. FIG. 10 is a diagram illustrating another configuration example of the inspection apparatus using the terahertz wave according to the second embodiment of the present invention. In the inspection apparatus shown in FIG. 10, a fixed delay reflection mirror 14 is installed between the beam splitter 2 and the terahertz wave receiving antenna 8 instead of the optical path adjustment unit 60.

  That is, the fixed delay reflection mirror 14 corresponds to the optical path adjustment unit of the present invention, and is formed by combining a plurality of mirrors having different thicknesses, and has a plurality of optical paths having different optical path lengths on the optical path of the second laser light. . Here, FIG. 11 is a diagram illustrating a configuration example of the fixed delay reflection mirror 14 in the inspection apparatus illustrated in FIG. 10. As shown in FIG. 11, the fixed delay reflecting mirror 14 has a stepped shape in order to generate a delay in the laser beam, and the width of each step is different by 0.435 mm. The inspection apparatus shown in FIG. 10 performs the same operation as that of the optical path adjustment unit 60 by rotating the fixed delay reflection mirror 14 in which the mirrors having different widths of 0.435 mm are rotated in this way. As in the case of the apparatus, the five points in FIG. 6 can be measured at the same time, and the physical quantity and physical properties of the measurement object 100 can be estimated with a short time measurement.

  The rotation period of the fixed delay reflection mirror 14 is 3.3 × NHz. Assuming that the time constant is 100 ms, the measurement interval is 300 ms as in the first embodiment, and it is necessary to always rotate the fixed delay reflection mirror 14 during this period. That is, the fixed delay reflection mirror 14 needs to rotate at 1/300 ms = 3.3 Hz or more. This is because if the rotation is less than 3.3 Hz, the next measurement starts before the fixed delay reflection mirror 14 makes one round. The rotation speed of the fixed delay reflection mirror 14 may be 3.3 × NHz.

  It is also conceivable to use a fixed delay reflecting mirror instead of the time delay mechanism 11. FIG. 12 is a diagram illustrating another configuration example of the inspection apparatus using the terahertz wave according to the second embodiment of the present invention. In the inspection apparatus shown in FIG. 12, fixed delay reflecting mirrors 14-1 and 14-2 are installed between the beam splitter 2 and the terahertz wave receiving antenna 8 instead of the time delay mechanism 11 and the optical path adjustment unit 60. .

  Here, FIG. 13 is a diagram illustrating a configuration example of the fixed delay reflection mirrors 14-1 and 14-2 in the inspection apparatus illustrated in FIG. The fixed delay reflection mirror 14-1 corresponds to the time delay unit of the present invention, and is formed by combining a plurality of mirrors having different thicknesses, and gives a time delay to the second laser light emitted from the beam splitter 2.

  That is, as shown in FIG. 13A, the fixed delay reflection mirror 14-1 is configured in a step shape so as to generate a delay in the second laser light. In order to measure as 7 ps, the width of the step differs by 40 μm. However, the width of the step is not necessarily 40 μm, and is preferably 40 μm or less. Further, the fixed delay reflection mirror 14-1 has at least 1024 steps. Thereby, 1024 points or more can be measured. For example, assuming that the time constant of the lock-in amplifier 51 is 1 s and it takes 3 s to measure each point, the fixed delay reflection mirror 14-1 needs to wait 3 s at each stage when rotating, so it is very slow. It will rotate at speed.

  Since the fixed delay reflecting mirror 14-1 is rotated to perform the same operation as the time delay mechanism 11, the inspection apparatus shown in FIG. 12 is used in combination with the fixed delay reflecting mirror 14-2 described later. As a result, as in the case of the inspection apparatus shown in FIG. 5, the five points in FIG. 6 can be measured simultaneously, and the physical quantity, physical properties, etc. of the measurement object 100 can be estimated in a short time measurement.

  On the other hand, the fixed delay reflection mirror 14-2 corresponds to the optical path adjustment unit of the present invention, and is formed by combining a plurality of mirrors having different thicknesses, and having a plurality of optical paths having different optical path lengths on the optical path of the second laser light. It is. As shown in FIG. 13B, the fixed delay reflection mirror 14-2 has a step shape for generating a delay in the laser light, and the width of the step differs by 0.435 mm.

  In this way, the fixed delay reflection mirror 14-2, which is a combination of mirrors having different widths by 0.435 mm, is rotated to perform the same operation as the optical path adjustment unit 60. Therefore, the inspection apparatus shown in FIG. As in the case of the illustrated inspection apparatus, the five points in FIG. 6 can be measured at the same time, and the physical quantity and physical properties of the measurement object 100 can be estimated with a short time measurement.

  FIG. 14 is a diagram illustrating a configuration of an inspection apparatus using a terahertz wave according to the third embodiment of the present invention. A difference from the configuration of the second embodiment illustrated in FIG. 5 is that a continuous delay reflection mirror 15 is provided instead of the optical path adjustment unit 60.

  FIG. 15 is a diagram showing a configuration of the continuous delay reflection mirror 15 in the inspection apparatus shown in FIG. However, although not shown in FIG. 14, a filter 24 is actually installed in front of the continuous delay reflection mirror 15. The continuous delay reflection mirror 15 and the filter 24 correspond to the optical path adjustment unit of the present invention, and have a plurality of optical paths having different optical path lengths on the optical path of the second laser light. The beam splitter 2 and the terahertz It is installed between the wave receiving antenna 8.

  Specifically, as shown in FIG. 15, the continuous delay reflection mirror 15 is a mirror whose thickness changes continuously. In other words, the continuous delay reflection mirror 15 is configured in a slope shape to generate a delay in the second laser light. Yes. Moreover, the filter 24 has a location for allowing the second laser beam to pass therethrough and a location for blocking the second laser beam.

  Other configurations are the same as those in the second embodiment, and a duplicate 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 inspection apparatus according to the second embodiment. For example, as in the case of the fixed delay reflection mirror 14 described with reference to FIG. 11, when measuring a place where the distance is different by 0.435 mm, the inspection apparatus of the present embodiment rotates the continuous delay reflection mirror 15 and the filter 24. Control is performed so that reflected light can be obtained by irradiating only a portion having a distance of 0.435 mm. Thereby, the continuous delay reflection mirror 15 and the filter 24 perform the same operation as the fixed delay reflection mirror 14 described in FIG.

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

  As described above, according to the inspection apparatus according to the third embodiment of the present invention, by including the continuous delay reflection mirror 15 and the filter 24, five points can be measured simultaneously as shown in FIG. Since the control range of the time delay mechanism 11 can be limited, the physical quantity, physical properties, etc. of the measurement object 100 can be estimated by measurement in a short time as in the second embodiment.

  As a modification, it is also conceivable to use a fixed delay transmission plate instead of the time delay mechanism 11. FIG. 16 is a diagram illustrating another configuration example of the inspection apparatus using the terahertz wave according to the third embodiment of the present invention. The inspection apparatus shown in FIG. 16 includes a fixed delay transmission plate 16 instead of the time delay mechanism 11 between the beam splitter 2 and the terahertz wave receiving antenna 8.

  Here, FIG. 17 is a diagram showing a configuration of the fixed delay transmission plate 16 in the inspection apparatus shown in FIG. The fixed delay transmission plate 16 corresponds to the time delay unit of the present invention, is configured by combining a plurality of transmission plates having different thicknesses, and gives a time delay to the second laser light emitted from the beam splitter 2. Specifically, the fixed delay transmission plate 16 has a stepped shape with different thicknesses as shown in FIG. 17 in order to delay the laser beam.

For example, consider a case where the fixed delay transmission plate 16 has a refractive index of 1.5 and measures 26.7 ps at the same time as in FIG. Since the refractive index is 1.5, the speed in the material through which the laser light passes through the fixed delay transmission plate 16 is 2 × 10 ⁸ m / s from V = c / n (V: speed of light in the material, c: Speed of light, n: refractive index). In order to measure 26.7 ps at a time, the thickness may be changed by 2 × 10 ⁸ m / s × 26.7 × 10 ⁻¹⁴ s / 2 = 26.7 μm.

  However, since the inspection apparatus shown in FIG. 16 does not have a configuration corresponding to the optical path adjustment unit of the present invention, the time delay mechanism 11 is replaced with the fixed delay transmission plate 16 and the operation described in the first embodiment is performed. Thus, the same effect as in the first embodiment can be obtained.

  In addition, a configuration corresponding to the optical path adjustment unit such as the fixed delay reflection mirror 14 and the continuous delay reflection mirror 15 may be incorporated into the inspection apparatus illustrated in FIG.

  The operation similar to that of the time delay mechanism 11 is performed by rotating the fixed delay transmission plate 16 in which a plurality of transmission plates (for example, 1024 sheets) each having a thickness of 26.7 μm are combined in this way. The apparatus can estimate the physical quantity, physical properties, and the like of the measurement object 100 with a short-time measurement, and can reduce the size of the apparatus.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Laser diode 2 Beam splitter 3 Mirror 4 Lens 5 Terahertz wave oscillation antennas 6 and 7 Parabolic mirror 8 Terahertz wave receiving antenna 9 Lens 10 Mirror 11 Time delay mechanism 12 Mirror 13 Multilayer film mirror 14, 14-1, 14-2 Fixed delay reflection mirror 15 Continuous delay reflection mirror 16 Fixed delay transmission plate 20 Electrode 21 Gap 22 Low temperature growth gallium arsenide substrate 23 Laser light 24 Filter 25 Silicon lens 50 Signal generator 51 Lock-in amplifier 52 Data holding unit 53 Display device 56 Data processing Unit 57 control unit 58 database 60 optical path adjustment unit 100 measurement object

Claims (7)

A light splitting section for splitting the laser light 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;
A time delay unit that gives a time delay to the second laser light emitted by the light splitting unit;
A terahertz wave oscillated by the terahertz wave oscillating unit is detected at a detection timing based on the second laser beam given a time delay by the time delay unit, and a detection signal corresponding to the intensity of the detected terahertz wave is generated. A terahertz wave detection unit;
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, and the time delay given by the time delay unit is changed A control unit that predicts a position where time-series signal intensity data based on a detection signal indicates a peak value, and controls a time delay range provided by the time delay unit based on the predicted position to a predetermined limited range;
Based on the peak value of 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 inspection unit for inspecting the characteristics of the measurement object;
A lock-in amplifier that amplifies the detection signal generated by the terahertz wave detection unit;
The control unit predicts a position where time-series signal intensity data shows a peak value based on a detection signal generated by the terahertz wave detection unit when a time constant of the lock-in amplifier has a first predetermined value,
The inspection unit controls the time delay range provided by the time delay unit to a predetermined limited range based on the position predicted by the control unit, and sets the time constant of the lock-in amplifier to a first predetermined value. When the terahertz wave is changed to a large second predetermined value, the characteristic of the measurement object is inspected based on the peak value of the signal intensity data based on the detection signal generated by the terahertz wave detection unit. Inspection device used. A light splitting section for splitting the laser light 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;
  A time delay unit that gives a time delay to the second laser light emitted by the light splitting unit;
  A terahertz wave oscillated by the terahertz wave oscillating unit is detected at a detection timing based on the second laser beam given a time delay by the time delay unit, and a detection signal corresponding to the intensity of the detected terahertz wave is generated. A terahertz wave detection unit;
  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, and the time delay given by the time delay unit is changed A control unit that predicts a position where time-series signal intensity data based on a detection signal indicates a peak value, and controls a time delay range provided by the time delay unit based on the predicted position to a predetermined limited range;
  Based on the peak value of 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 inspection unit for inspecting the characteristics of the measurement object,
  The control unit installs a measurement object in the terahertz waveguide between the terahertz wave oscillating unit and the terahertz wave detecting unit based on a position where the time series signal intensity data of the reference measured in advance shows a peak value. Terahertz, wherein the time-series signal intensity data based on the detection signal generated by the terahertz wave detection unit when the time delay given by the time delay unit is changed predicts a position where the peak value is shown. Inspection equipment using waves. A light splitting section for splitting the laser light 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;
  A time delay unit that gives a time delay to the second laser light emitted by the light splitting unit;
  A terahertz wave oscillated by the terahertz wave oscillating unit is detected at a detection timing based on the second laser beam given a time delay by the time delay unit, and a detection signal corresponding to the intensity of the detected terahertz wave is generated. A terahertz wave detection unit;
  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, and the time delay given by the time delay unit is changed A control unit that predicts a position where time-series signal intensity data based on a detection signal indicates a peak value, and controls a time delay range provided by the time delay unit based on the predicted position to a predetermined limited range;
  Based on the peak value of 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 inspection unit for inspecting the characteristics of the measurement object,
The control unit, based on the refractive index and thickness of the sample case into which the measurement object is placed, installs the measurement object in the terahertz waveguide between the terahertz wave oscillation unit and the terahertz wave detection unit, A terahertz wave characterized by predicting a position where time-series signal intensity data based on a detection signal generated by the terahertz wave detection unit when the time delay given by the time delay unit is changed shows a peak value. Inspection device used. 4. The optical path adjusting unit according to claim 1, further comprising: an optical path adjusting unit having a plurality of optical paths having different optical path lengths on at least one of the first laser light and the second laser light. Inspection apparatus using the terahertz wave described in the item. 5. The inspection apparatus using terahertz waves according to claim 4, wherein the optical path adjustment unit is configured by a multilayer mirror. The inspection apparatus using a terahertz wave according to any one of claims 1 to 5, wherein the time delay unit is configured by a fixed delay transmission plate in which a plurality of transmission plates having different thicknesses are combined. . A light splitting step for splitting the laser light into a first laser light and a second laser light;
  A terahertz wave oscillating step of oscillating a terahertz wave by being irradiated with the first laser light emitted by the light splitting step;
  A time delay step of giving a time delay to the second laser light emitted by the light splitting step;
  The terahertz wave oscillated by the terahertz wave oscillating step is detected at a detection timing based on the second laser beam given the time delay by the time delay step, and a detection signal corresponding to the intensity of the detected terahertz wave is generated. Terahertz wave detection step;
  Position where the measurement object is placed in the terahertz waveguide and the time-series signal intensity data based on the detection signal generated by the terahertz wave detection step when the time delay given by the time delay step is changed shows the peak value A control step for controlling the range of the time delay given by the time delay step to a predetermined limited range based on the predicted position;
  An inspection step of inspecting characteristics of the measurement object based on a peak value of signal intensity data based on the detection signal generated by the terahertz wave detection step when the measurement object is installed in the terahertz waveguide;
  A lock-in amplifier that amplifies the detection signal generated by the terahertz wave detection step;
  The control step predicts a position where the time-series signal intensity data shows a peak value based on the detection signal generated by the terahertz wave detection step when the time constant of the lock-in amplifier has a first predetermined value;
  The inspection step controls the time delay range given by the time delay step to a predetermined limited range based on the position predicted by the control step, and sets the time constant of the lock-in amplifier to be less than a first predetermined value. When the terahertz wave is changed to a large second predetermined value, the characteristic of the measurement object is inspected based on the peak value of the signal intensity data based on the detection signal generated by the terahertz wave detection step. Inspection method used.

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