JP4654996B2 - Terahertz wave response measuring device - Google Patents

Description

  The present invention relates to a terahertz wave response measuring apparatus that can be used in a spectroscopic analysis apparatus, a fluoroscopic apparatus, and the like using a terahertz (THz) wave.

  Conventionally, as an analysis method using terahertz waves, terahertz time domain spectroscopy (THz-TDS) using a so-called femtosecond laser having a pulse width of less than 1 psec and a repetition frequency of several tens of MHz has been widely known. (See Patent Document 1, Non-Patent Documents 1 and 2, etc.) Furthermore, devices using this method have already been commercialized (see Non-Patent Document 4 and the like). In addition, because femtosecond laser light sources are expensive, the same analysis as terahertz time-domain spectroscopy using multimode lasers instead of femtosecond lasers to generate terahertz waves mainly aimed at lowering costs Attempts have also been made (see Non-Patent Document 3, etc.). Hereinafter, for convenience of explanation, an apparatus using terahertz time domain spectroscopy will be described.

  4 and 5 are configuration diagrams of a main part of a conventional analyzer using terahertz time-domain spectroscopy. FIG. 4 is based on a so-called step scan method, and FIG. 5 is based on a so-called rapid scan method. FIGS. 6 and 7 are diagrams for explaining the operation of the analyzers of FIGS. 4 and 5, respectively. First, based on FIG.4 and FIG.6, the structure and operation | movement of a terahertz time domain spectroscopic analyzer of a step scan system are demonstrated.

  The laser light source 1 emits femtosecond laser light, which is split by the beam splitter 2 into two laser light, that is, pump (excitation) light 3 and probe light 4, and the pump light 3 is reflected by the reflecting mirror 5. And introduced into the optical path length scanning unit 6. The optical path length scanning unit 6 has a configuration in which the optical path length is changed by mechanically scanning the position of the movable mirror 6a by a drive mechanism 7 including a motor or the like. The pump light 3) is reflected by the reflecting mirror 5 and sent to the transmitter 9. The transmitter 9 is a source that generates terahertz waves when excited by femtosecond laser light. As described in Non-Patent Documents 1 and 2, for example, a method using a semiconductor photoconductive antenna, a nonlinear optical crystal Various methods such as a method of using can be used.

  The terahertz wave 10 emitted from the transmission unit 9 is irradiated to the sample S through a terahertz wave optical system 11 configured by a parabolic mirror, and the terahertz wave 10 ′ transmitted through the sample S passes through the terahertz wave optical system 11. Guided to the receiver 12. On the other hand, the probe light 4 branched by the beam splitter 2 reaches the receiving unit 12 through the reflecting mirror 13 and the optical path length adjusting unit 14 having a fixed optical path length. The receiving unit 12 receives the terahertz wave 10 ′ and the femtosecond laser light (probe light 4), detects the time integral of the product of the electric field of the terahertz light 10 ′ and the intensity of the probe light 4, and outputs it as an analog detection signal. To do. Specifically, as described in Non-Patent Documents 1 and 2 and the like, the detection signal as described above is generated using various methods such as a method using a photoconductive antenna and an electro-optic effect sampling method. Can be generated.

  Terahertz time domain spectroscopy is a method of sampling the detection signal of the receiver 12 corresponding to the instantaneous electric field of the terahertz wave as a function of the optical delay distance (the amount of displacement of the optical path length) corresponding to the propagation time of the terahertz wave. It is necessary to obtain accurate information on the displacement of the optical distance of the optical path length scanning unit 6 at each sampling timing. Further, in the arithmetic processing for obtaining a frequency spectrum by performing Fourier transform on the time change of the terahertz wave electric field performed later in the control / processing unit 23, detection of the receiving unit 12 sampled at every constant displacement interval of the optical distance of the optical path length scanning unit 6. A signal (measurement data) is required.

  In order to obtain such measurement data, in the step scan method, the movable mirror 6a of the optical path length scanning unit 6 is scanned at a considerably slow speed (usually taking a time of 1 second or more). That is, when the control / processing unit 23 sends a control signal for such scanning to the servo mechanism 30, the servo mechanism 30 monitors the displacement signal 32 indicating the displacement amount and position of the movable mirror 6a by the displacement meter 31, and the target displacement. The operation of the drive mechanism 7 is controlled by closed loop control so that the error between the amount and the actual displacement amount becomes zero. For example, as shown in FIG. 6A, the optical path length scanning unit 6 is driven so that the optical path length changes stepwise by a certain distance using the maximum variable range L of the optical path length as the scanning range. That is, the movement of the movable mirror 6a moving by a predetermined distance and temporarily stopped at that position is repeated. As a whole, the scanning of the movable mirror 6a is slow, but each position when stopped is controlled with high accuracy.

  As described above, every time the movable mirror 6a moves to each position in one scan, the control / processing unit 23 sends the sampling pulse signal 33 to the sample / hold (S / H) circuit 20 and the integrating circuit 34. . The integrating circuit 34 is an amplifier that integrates the analog detection signal output from the receiving unit 12 during the pulse interval of the sampling pulse signal 33, and the sample / hold circuit 20 samples the integrated analog value. In this case, since one scanning time is relatively long and the stop time of the movable mirror 6a at each position within the scanning range is also long, the integration circuit 34 fully integrates the analog detection signals output from the receiving unit 12. Thus, the S / N ratio can be improved, and this can be sampled and converted into a digital value by the A / D converter 21. Then, the measurement data converted into the digital value is sent to the control / processing unit 23 and used for arithmetic processing such as Fourier transform.

  As described above, in the scan step method, since the detection signals of the receiving unit 12 are integrated and averaged at each position when the optical path length is scanned once, the SN ratio can be increased thereby. However, if one scanning time is long, the femtosecond laser is likely to be affected by intensity fluctuations in a long time order of 1 second or more. There is a possibility that the radiation field intensity of the terahertz wave differs. Therefore, there is a drawback that the frequency spectrum shape of the terahertz wave response to the sample S is easily distorted.

  Conventionally, the step scan method has been mainstream, but due to the above drawbacks, recently, the optical path length scanning unit 6 is normally continuously scanned with a repetition period of 2 Hz or more, and is output from the receiving unit 12 by a plurality of scans. The so-called rapid scan method, which takes an average of detected signals, is becoming mainstream. The configuration and operation of a rapid scan terahertz time domain spectroscopic analyzer will be described with reference to FIGS. The same components as those in the step scan type apparatus shown in FIG.

  In the rapid scan method, since the optical path length is changed at a higher speed than in the step scan method, it is difficult to perform step-like scanning with accurate position control. For example, as shown in FIG. The control / processing unit 23 controls the drive mechanism 7 so that the mirror 6a is repeatedly reciprocated. On the other hand, the control / processing unit 23 sends a sampling pulse signal 33 having a constant time interval Δt2 that is much shorter than that in the scan step method to the sample / hold circuit 20 and is synchronized with this pulse signal by the receiving unit 12. The detection signal is sampled and converted into a digital value. Further, a displacement signal 32 detected by the displacement meter 31 and indicating the displacement of the movable mirror 6 a in the optical path length scanning unit 6 is input to the control / processing unit 23.

  In the rapid scan method, measurement data at the same position is obtained many times by repeated scanning, and therefore the SN ratio can be improved by performing a process of integrating a plurality of measurement data at each position. In addition, even if the intensity of the femtosecond laser fluctuates with time, the influence does not shift to a specific position, so that there is an advantage that the influence of such fluctuation is less likely. In this way, the rapid scan method is superior to the step scan method in that it is hardly affected by the fluctuation of the femtosecond laser. However, the conventional rapid scan method has the following problems.

  That is, the sample / hold circuit 20 samples the detection signal from the receiving unit 12 at a constant time interval Δt2, but if the movable mirror 6a can be accurately moved at a constant speed, the sampling interval becomes an equal displacement interval. It is a spear. However, when the movable mirror 6a is repeatedly reciprocated at high speed, complete uniform speed movement is quite difficult, and the load on the drive mechanism 7 is large and the cost is high. Therefore, in a general configuration, for example, the servo mechanism 30 is used to perform speed control so that the moving speed of the movable mirror 6a is approximately constant near the center of the scanning range, and gradually becomes zero near the turning position. A method of sampling only near the center of the scanning range is adopted. However, even if the section is limited to the vicinity of the center of the scanning range in this way, it is impossible to realize a strict constant velocity motion due to the limit of the performance of the servo mechanism 30 (for example, followability). When the movable mirror 6a is not moved at a constant speed, the sampling at the constant time interval Δt2 is not a sampling at every constant displacement interval. Therefore, it is necessary for the control / processing unit 23 to interpolate the measurement data based on the information of the displacement signal 32 and calculate the measurement data for each constant displacement interval. By performing such correction processing, degradation of signal accuracy is unavoidable, and there is a disadvantage that measurement time is prolonged due to the time required for the arithmetic processing.

JP 2005-129732 A Masanori Tomoyuki, “Terahertz and Far-Infrared Spectroscopy III. Ultrafast Spectroscopy”, Spectroscopical Society of Japan, Spectroscopic Research, Vol. 54, No. 3 (2005), p.181-198 Masaya Nagai and Koichiro Tanaka, “Basics and Applications of Terahertz Time Domain Spectroscopy”, Japan Society of Applied Physics, Applied Physics, Vol. 75, No. 2 (2006), p.179-187 O. Morikawa and two others, "Improvement of signal-to-noise ratio of a sub-terahertz spectrometer, using a continuous-wave multimode laser diode・ Improvement of signal-to-noise ratio of a subterahertz spectometer using a continuous-wave multimode laser diode by single-mode fiber optics ”, Applied Physics Letters (Appl. Phys. lett.), Vol.85, No.6, 2004-8-9, p.881-883 "Terahertz Pulse Spectrometer", [online], Tochigi Nikon Corporation, [searched July 6, 2006], Internet <URL: http://www.tochigi-nikon.co.jp/>

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to eliminate the need for arithmetic processing that leads to a decrease in accuracy such as interpolation processing while taking advantage of the rapid scan method. An object of the present invention is to provide a terahertz wave response measuring apparatus that can ensure high signal accuracy and avoid prolonged measurement time.

The present invention, which has been made to solve the above problems, includes a laser light source, terahertz wave generating means for generating terahertz waves upon irradiation with laser light emitted from the laser light source, and generated by the terahertz wave generating means A terahertz wave optical system that irradiates the sample with a terahertz wave that is reflected or transmitted by the sample and guides the terahertz wave to the detection means described later, and the terahertz wave that has arrived from the sample by the terahertz wave optical system and the laser light And a detection means for outputting a detection signal based on the electric field of the terahertz wave and the intensity of the laser light, and a first optical path from the laser light source to the terahertz wave generation means or the detection means from the laser light source An optical path length scanning means for changing the optical path length of any one of the second optical paths up to and including the optical path length changing means by the optical path length scanning means In the terahertz wave response measuring device for obtaining information on the sample based on a detection signal from said detecting means at the time of,
a) control means for controlling the optical path length scanning means to repeatedly and continuously scan the optical path length of the first optical path or the second optical path;
b) Displacement detecting means for outputting a pulse signal every time when the displacement of the optical path length occurs during the repeated scanning by the control means;
c) signal conversion means for sampling the analog detection signal by the detection means and converting it into a digital value, the signal conversion means for sampling in synchronization with the pulse signal by the displacement detection means or a pulse signal derived therefrom;
It is characterized by having.

  Here, it is assumed that the laser light source emits a laser beam that has a part or all of the frequency components in the frequency range of 10 GHz to 20 THz and changes in intensity. A typical femtosecond laser is a so-called femtosecond laser. However, if the laser fluctuates on the same time scale, for example, a CW multimode laser whose intensity fluctuates at picosecond time levels due to interference between modes may be used. It may be used.

  Further, the terahertz wave generation method by the terahertz generation means and the detection method of the terahertz wave electric field change by the detection means are not particularly limited, and various generally proposed methods can be used.

  For example, as disclosed in “Non-Patent Document 4” as “real-time terahertz imaging”, a configuration in which a two-dimensional detection device such as a CCD camera is used as the detection means is also conceivable. In such a charge accumulation type device, the sampling timing is determined by the charge accumulation timing in the detection unit. Therefore, in the configuration using such a detection means, the signal conversion means in the above-mentioned signal conversion means “the pulse signal from the displacement detection means or derived therefrom. “Sampling in synchronization with the pulse signal to be performed” can be replaced with “determining the timing of charge accumulation in the detection means in synchronization with the pulse signal from the displacement detection means or a pulse signal derived therefrom”.

  Here, the “pulse signal derived from it” is a pulse obtained by delaying the pulse signal generated by dividing the pulse signal by the displacement detecting means or the pulse detecting means by the displacement detecting means, as will be described later, for example. Refers to the signal.

  In the terahertz wave response measuring apparatus according to the present invention, the optical path length scanning unit repeatedly scans, for example, the optical path length of the first optical path (or the second optical path) under the control of the control unit. For example, if the variable range of the optical path length is L, reciprocating scanning is repeated in the range of 0 to L. The scanning speed at that time may be constant or non-constant. When this scanning is being performed, the displacement detection means outputs a pulse signal every time a certain amount of optical path length displacement occurs. That is, when the variable range of the optical path length is L as described above, a pulse signal is generated every time the optical path length changes by a displacement interval ΔL sufficiently smaller than L. The signal conversion means samples the analog detection signal by the detection means in synchronization with the pulse signal itself or a pulse signal derived therefrom, and converts the sample value into a digital value to obtain measurement data.

  As one aspect of the terahertz wave response measuring apparatus according to the present invention, it is associated with displacement position information based on a displacement amount detection signal obtained by the displacement detection means based on the pulse signal from the displacement detection means or separately from the pulse signal. The measurement data can be stored in the storage means. Here, the displacement position information is information indicating a position obtained by dividing the variable range L of the optical path length at a certain distance, and may be, for example, a number assigned in order from one end of the variable range.

  By storing the measurement data in the storage means in association with the displacement position information in this way, for example, after collecting all the measurement data once, a plurality of measurement data corresponding to the same displacement position information is integrated, integrated average By performing the conversion processing or the like, it is possible to improve the SN ratio of the measurement data (detection signal by the detection means), and to improve the accuracy of the frequency spectrum obtained by Fourier calculation based on this.

  In the terahertz wave response measuring apparatus according to the present invention, the displacement detecting means may be any means capable of detecting the optical path length changed by the optical path length scanning means, typically the position of the reflector moved mechanically. It is possible to use a magnetic linear scale, an optical linear scale, a distance meter, or the like, but a laser interferometer is preferably used from the viewpoint of accuracy. In a laser interferometer, a He—Ne laser beam or the like is split into two light beams, and one light beam is incident on an optical path length scanning means (for example, a moving mirror) to receive the reflected light. The reflected light and the other light beam Are combined to detect an interference signal corresponding to the difference between the two optical path lengths. This makes it possible to generate an interference signal in which the intensity of interference appears every time the optical path length scanning means (moving mirror) moves by a certain distance. Therefore, the pulse signal obtained by digitizing the laser interference detection signal or the pulse signal is separated. The pulse signal obtained by the rotation can be supplied as a pulse signal for sampling in the signal conversion means.

  Since the signal detected by the detection means is weak, the detection means usually includes an amplifier having a relatively large gain. However, when the gain is increased in such an amplifier, the time constant increases and the signal delay increases. If the time delay of the detection signal becomes so large that it cannot be ignored compared to the sampling time interval, the time lag between the displacement position information by the optical path length scanning means and the input signal to the signal conversion means becomes large, and the correspondence between the two is accurate. There is a risk that it will disappear. In order to eliminate the time lag, the pulse signal output from the displacement detection means corresponds to the time delay in the detection means, since it is not possible to give time advance to the signal that has caused the time delay in the detection means. A configuration including delay means for delaying by time is preferable. Thereby, measurement data accurately associated with the displacement position information obtained by the optical path length scanning unit can be obtained.

  However, since it is desirable to change the gain of the amplifier included in the detection means in accordance with conditions such as the type of sample and the purpose of measurement, it is preferable to make the delay time variable so that the delay time in the delay means can be adjusted accordingly.

  According to the terahertz wave response measuring apparatus according to the present invention, the detection signal accurately obtained at every constant displacement interval regardless of whether the optical path length (optical distance) displacement by the optical path length scanning means is constant speed or non-constant speed. Measurement data based on can be collected. As a result, it is not necessary to perform a calculation process for interpolating measurement data in order to eliminate a shift in the displacement interval as in the prior art, and a decrease in accuracy due to such a process can be avoided. Further, by omitting unnecessary calculation processing, it is possible to shorten the time until an originally necessary result such as a frequency spectrum is obtained.

  A terahertz time domain spectroscopic analyzer which is an embodiment of a terahertz wave response measuring apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a main part of the terahertz time domain spectroscopic analyzer according to the present embodiment, and the same components as those in FIGS. 4 and 5 described above are denoted by the same reference numerals. 2 and 3 are diagrams for explaining the optical path length scanning and the sampling operation in the terahertz time domain spectroscopic analyzer according to this embodiment.

  In the terahertz time domain spectroscopic analysis apparatus according to the present embodiment, a detection signal is obtained at the receiving unit 12 with repeated reciprocating scanning of the movable mirror 6a in the optical path length scanning unit 6 in the conventional rapid scan system (see FIG. 5). Configuration). However, the operation for sampling the analog detection signal output from the receiving unit 12 and collecting measurement data obtained by digitizing each sample is greatly different. This point will be described in detail below.

  In accordance with the amplitude / frequency control signal 25 output from the control / processing unit 23, the driving mechanism 7 drives the movable mirror 6a of the optical path length scanning unit 6, and thereby the optical path length of the laser beam (pump light 3) (in the present invention). The optical path length of the first optical path changes. Here, as shown in FIG. 2A, scanning is performed so that the velocity changes sinusoidally, that is, the movable mirror 6a is moved at a non-constant speed. As a result, the speed drops at the end of the scanning range, and the load on the drive mechanism 7 can be light. A laser interferometer 8 is attached to the optical path length scanning unit 6 in order to detect the position of the movable mirror 6 a, that is, the displacement of the optical path length until the pump light 3 reaches the transmission unit 9.

  The laser interferometer 8 includes a He—Ne laser light source, the laser light emitted from the laser light source is split into two light beams by a beam splitter, and one of the light beams is irradiated onto the moving mirror 6a to obtain the reflected light. The other branched light beam is introduced into a 45 ° prism, and the phase of p-polarized light and s-polarized light is shifted by 90 ° when reflected by the prism by 180 °. When the two light beams that have returned to the beam splitter are merged, strength is generated by interference according to the difference in the optical path lengths of the two light beams. By appropriately designing the optical path, the signal intensity can be increased or decreased each time the movable mirror 6a moves by a certain distance, and this laser interference detection signal is shaped and binarized. Each time the optical path length of the pump light 3 changes by a certain distance, a pulse signal having a rising edge (or falling edge) can be generated. Here, the pulse signal 15 is output from the laser interferometer 8 and sent to the delay unit 17. Further, the p-polarized light and the s-polarized light are separated and detected from the laser light combined by the beam splitter, and the phase relationship is examined, so that the moving direction of the moving mirror 6a (that is, the optical path length increases or decreases). Whether or not the direction is changed) is detected and output as a polarity signal 16 to be sent to the delay unit 18.

  A magnetic linear scale, an optical linear scale, or the like may be used instead of the laser interferometer 8, but the laser interferometer 8 is desirable in terms of position resolution and high accuracy.

  As described above, since the laser interferometer 8 outputs the pulse signal 15 every time the optical path length of the pump light 3 changes by a certain distance, as shown in FIG. 2A, when the optical path length change is sinusoidal. That is, when the movement of the movable mirror 6a is non-constant, the generation interval of the pulse signal 15 is a non-constant time interval. That is, with respect to scanning of the optical path length, the pulse signal 15 is generated at a constant displacement interval ΔL spatially, and the generation interval of the pulse signal is non-constant in time.

  Each of the delay units 17 and 18 delays an input signal by a predetermined time and outputs it, and the delay time is set so as to correspond to a time delay in an analog electric circuit (mainly an amplifier) included in the receiving unit 12. Is done. The delay time in the delay units 17 and 18 can be arbitrarily set within a predetermined range. This is because the amplification factor of the amplifier included in the receiving unit 12 is variable, and the time delay varies depending on the amplification factor, and the delay time in the delay units 17 and 18 is adjusted according to the time delay. Thus, the sampling timing described later can be accurately adjusted. Although the delay units 17 and 18 may be analog delay circuits, a digital delay circuit is used in order to avoid dull waveform of the pulse signal when the delay time is increased and to easily adjust the delay time as described above. It is preferable to do this.

  The pulse signal 15 ′ added with a predetermined time delay by the delay unit 17 is supplied to the sample / hold circuit 20 as a sampling pulse signal. Therefore, the sample / hold circuit 20 samples the analog detection signal 19 output from the receiver 12 at the timing shown in FIG. 2B, and converts the sample value into a digital signal by the A / D converter 21. And output. That is, the analog detection signal 19 is sampled at non-constant time intervals. This is completely different from the sampling in the conventional rapid scan method. Each time the pulse signal 15 ′ is input to the sample / hold circuit 20, one digitized measurement data is supplied to the control / processing unit 23.

  Further, the pulse signal 15 ′ to which the time delay is added and the polarity signal 16 ′ to which the time delay is also added are input to the counter circuit (CNT) 22, where it is converted into position information within the scanning range L. For example, when the optical path length is changing in the increasing direction, it is counted up every time the pulse signal 15 'is input, and when the optical path length is changing in the decreasing direction, it is counted down every time the pulse signal 15' is input. In addition, the count value can be extracted as position information. In the control / processing unit 23, the measurement data obtained from the A / D conversion unit 21 is sequentially stored in the internal data storage unit 24 in association with the position information obtained from the counter circuit 22.

  By the above processing, as shown in FIG. 3A, position information P0, P1,..., Pn is given for each constant displacement interval ΔL within the scanning range L of the optical path length, and reciprocating scanning is executed a plurality of times. In the process, as shown in FIG. 3B, measurement data is acquired corresponding to each position to which position information is given. When the count value of the counter circuit 22 is position information P0, P1,..., Pn, the position information is 0, 1, 2,. Since n + 1 pieces of measurement data obtained by one-way scanning have accurate position information for each constant displacement interval ΔL, a plurality of pieces of measurement data having the same position information can be obtained without correcting such positional deviation. An integrated averaging process can be performed on the measured data.

  As described above, the terahertz time domain spectroscopic analyzer according to the present embodiment can accurately collect measurement data to be subjected to the Fourier transform process while scanning the optical path length at high speed and non-constant speed.

  In the configuration shown in FIG. 1, the terahertz wave 10 is irradiated onto the sample S with a parallel light beam and the transmitted wave is detected, but the form in which the terahertz wave 10 is irradiated onto the sample S is a parallel light beam. Not limited to this, a convergent light beam is also possible. Moreover, the optical arrangement which detects not only the transmitted wave of the sample S but a reflected wave or a scattered wave may be sufficient.

  Further, it is desirable that the displacement interval ΔL of the optical path length at which the laser interferometer 8 or a displacement meter corresponding thereto outputs the pulse signal 15 is variable by setting from the outside. This makes it possible to optimize the scanning range L of the optical path length scanning unit 6 and the number of sampling points per scan according to the desired measurement conditions. Specifically, for example, when the laser interferometer 8 is used, the laser interference detection signal divided by the frequency dividing circuit is output as the pulse signal 15, and the frequency dividing ratio of the frequency dividing circuit can be arbitrarily set. It is good to do so.

  In addition, the configuration (means) for creating position information based on a signal output from the laser interferometer 8 or a displacement meter corresponding thereto is not limited to the above description. For example, the displacement meter outputs a displacement signal reflecting the displacement amount in addition to the pulse signal and the polarity signal as described above, and the control / processing unit 23 that receives the displacement signal calculates the displacement amount and performs the above processing. It is good also as a structure which calculates the same positional information.

  Further, in the configuration of the above embodiment, the optical path length of the optical path of the pump light 3 is scanned. As is apparent from the prior art, the same measurement can be performed by scanning the optical path length of the optical path of the probe light 4. is there.

  Further, the above embodiment is an embodiment of the present invention, and in addition to the above-described various modifications, any appropriate modifications, corrections, and additions within the scope of the present invention are included in the scope of the claims of the present application. Is natural.

The block diagram of the principal part of the terahertz wave time-domain spectroscopy analyzer by one Example of this invention. The figure for demonstrating the scanning and sampling operation | movement of the optical path length in the terahertz time-domain spectroscopy analyzer by a present Example. The figure for demonstrating the scanning and sampling operation | movement of the optical path length in the terahertz time-domain spectroscopy analyzer by a present Example. The block diagram of the principal part of the terahertz time domain spectroscopic analyzer of the conventional step scan system. The block diagram of the principal part of the conventional terahertz time domain spectroscopic analyzer of a rapid scan system. FIG. 5 is a diagram for explaining the operation of the step-scan terahertz time domain spectroscopic analysis apparatus shown in FIG. 4. The figure for demonstrating operation | movement of the terahertz time-domain spectroscopy analyzer of the rapid scan system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser light source 2 ... Beam splitter 3 ... Pump light 4 ... Probe light 5 ... Reflection mirror 6 ... Optical path length scanning part 6a ... Moving mirror 7 ... Drive mechanism 8 ... Laser interferometer 9 ... Transmission part 10, 10 '... Terahertz wave DESCRIPTION OF SYMBOLS 11 ... Terahertz wave optical system 12 ... Reception part 13 ... Reflector 14 ... Optical path length adjustment part 15, 15 '... Pulse signal 16, 16' ... Polarity signal 17, 18 ... Delay part 19 ... Analog detection signal 20 ... Sample / hold Circuit 21 ... A / D converter 22 ... Counter circuit 23 ... Control / processing unit 24 ... Data storage unit 25 ... Amplitude / frequency control signal S ... Sample

Claims (5)

A laser light source, terahertz wave generating means for generating a terahertz wave upon irradiation of laser light emitted from the laser light source, and irradiating the sample with the terahertz wave generated by the terahertz wave generating means and reflecting it by the sample A terahertz wave optical system that guides the transmitted or transmitted terahertz wave to the detection means described below, and the terahertz wave optical system receives the terahertz wave and the laser light that have arrived from the sample by the terahertz wave optical system, respectively, and the electric field of the terahertz wave and the laser light Detecting means for outputting a detection signal based on the intensity of the light, and changing the optical path length of either the first optical path from the laser light source to the terahertz wave generating means or the second optical path from the laser light source to the detecting means And an optical path length scanning unit for causing the optical path length scanning unit to change the optical path length based on a detection signal from the detection unit. In the terahertz wave response measuring device for obtaining information about the sample Te,
a) control means for controlling the optical path length scanning means to repeatedly and continuously scan the optical path length of the first optical path or the second optical path;
b) Displacement detecting means for outputting a pulse signal every time when the displacement of the optical path length occurs during the repeated scanning by the control means;
c) signal conversion means for sampling the analog detection signal by the detection means and converting it into a digital value, the signal conversion means for sampling in synchronization with the pulse signal by the displacement detection means or a pulse signal derived therefrom;
A terahertz wave response measuring apparatus comprising:   A memory for storing data output by the signal conversion means in association with displacement position information based on a displacement amount detection signal obtained from the displacement detection means based on a pulse signal from the displacement detection means or separately from the pulse signal The terahertz wave response measuring apparatus according to claim 1, comprising means.   The displacement detection means is a laser interferometer, and a pulse signal obtained by digitizing a laser interference detection signal from the laser interferometer or a pulse signal obtained by dividing the pulse signal is used for sampling in the signal conversion means. The terahertz wave response measuring apparatus according to claim 1, wherein the terahertz wave response measuring apparatus is supplied as a pulse signal.   The terahertz wave response measuring apparatus according to any one of claims 1 to 3, further comprising delay means for delaying a pulse signal output from the displacement detection means by a time corresponding to a time delay in the detection means. . The terahertz wave response measuring apparatus according to claim 4, wherein the delay unit has a variable delay time.

Images