JP2810798B2 - Time-resolved Fourier spectroscopy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating a stimulus periodically by a stimulus generating means and repeatedly applying the stimulus to a measurement object, and sampling a detector output using a rapid scan interferometer at a predetermined delay time after the stimulus. Time-resolved Fourier spectroscopy to measure the state of the spectrum in the reaction process of a measurement object that repeatedly shows the same response to a stimulus by acquiring an interferogram for a predetermined delay time and obtaining a spectrum by Fourier transform About the law.

[0002]

2. Description of the Related Art In the process of periodically applying a stimulus to a sample by means of electricity, a laser or other means and recovering from the stimulus, the need to measure the state of the reaction is, for example, when evaluating the characteristics of a liquid crystal, or in other cases. In various fields. As a measuring method, there is a time-resolved Fourier spectrometry using an FT-IR (Fourier transform infrared spectrophotometer). Since this method can measure a wide wavenumber range with a high SN ratio, it has been conventionally developed and used. However, it can be classified into a method using a rapid scan interferometer and a method using a step scan interferometer.

[0003] The FT-IR uses a Michelson interferometer comprising a semi-transmissive mirror, a movable mirror and a fixed mirror to obtain an interferogram by moving the movable mirror. There is a condition that the characteristics must be constant during the measurement, and if the characteristics of the sample change, information that is different from the original information will be output when the sample is subjected to Fourier transform. Therefore, in the time-resolved Fourier spectrometry, the period of the applied stimulus is required to be longer than the time when the reaction ends, but when applying the periodic stimulus, the stimulus is applied regardless of the movement of the movable mirror. , It is necessary to adopt that alignment. Therefore, conventionally, a stimulus is applied in synchronization with the reference signal of the interferometer.

Under such circumstances, the present applicant has already applied a stimulus to the object to be measured repeatedly by the stimulus generating means at a period longer than its response period, and the constant is smaller than the stimulus from the output of the detector using the rapid scan interferometer. A time-resolved spectrometry method that obtains an interferogram with respect to the delay time of a target and obtains a spectrum by Fourier transform, thereby measuring a reaction state of a measurement target that repeatedly shows the same response to the stimulus. Sampling is performed at a later fixed delay time, and the envelope of the sampled signal is obtained through a low-pass filter. Light is emitted from the light source, and the envelope of the obtained detector output signal is low-pass filtered. Through by determined, proposed a time-resolved spectroscopic measurement method characterized by obtaining the interferograms for the delay time with more stimulation (Japanese Patent Application No. 1-230209, Hei 2-82126～7
issue). In this method, the stimulus can be given asynchronously with the reference signal of the interferometer, so that the constraint on the stimulus can be greatly eased. Efficiency can be improved, and a series of time-series spectra of each delay time is obtained by repeating the same measurement while controlling the delay time of the gate circuit or the delay time of the pulse light source that samples the detector output. Is what you can do.

[0005] Further, a common light source to a detector is used for one measurement object, and a plurality of measurement systems for the specific delay time as described above are provided in parallel with different delay times to provide a stimulus to the stimulus. On the other hand, it has also been proposed to simultaneously measure the reaction states of a plurality of delay times of a measurement object showing the same response repeatedly (Japanese Patent Application No. 2-259355-6).
issue).

[0006]

However, according to the proposals by the present applicant, in any case, the reaction cycle of the measurement target is twice the maximum frequency f _max of the interferogram signal by the sampling theorem. Was assumed to be shorter than the reciprocal of. Assuming that the repetition period of the stimulus is τ, the above is τ <１ ／ f _max or f _max <１ ／
This means that τ was assumed.

The present invention has been made in view of such a situation, and an object of the present invention is to provide the above-described time-resolved Fourier spectroscopic measurement method proposed by the present applicant by using the time-resolved Fourier spectroscopy method in which the repetition period of the stimulus has the interferogram signal. Maximum frequency f
_In the case of a measurement longer than the reciprocal of twice _max , that is, to be applicable to a measurement object having a longer response cycle to a stimulus.

[0008]

According to the first time-resolved Fourier spectrometry of the present invention, which achieves the above object, a stimulus is repeatedly given by a stimulus generating means at a period longer than a reaction period of a measurement object, and a rapid scan interferometer is provided. Time-resolved Fourier spectroscopy that obtains the interferogram for a certain delay time from the stimulus from the output of the detector using the FIR, and obtains the spectrum by Fourier transform, thereby measuring the reaction state of the measurement object that shows the same response repeatedly to the stimulus A method wherein the modulation frequency by the interferometer is f and the repetition frequency of the stimulus is 1 / τ, where m / 2τ <f <(m + 1) /
In a time-resolved Fourier spectroscopy method applied when a detector output signal exists only at 2τ (m is a positive integer),
The detector output is sampled at a fixed delay time after the stimulus, a frequency component in the range of f <1 / 2τ of the sampled signal is extracted, and a phase correction is performed to obtain an interferogram for a delay time from the stimulus. It is a method characterized by acquiring.

In the second time-resolved Fourier spectroscopic measurement method, a stimulus is repeatedly given by a stimulus generating means at a period longer than a reaction period of an object to be measured, and a constant delay from the stimulus is obtained from a detector output using a rapid scan interferometer. A time-resolved Fourier spectroscopy method for measuring a reaction state of a measurement object that repeatedly shows the same response to a stimulus by acquiring an interferogram with respect to time and obtaining a spectrum by Fourier transform, wherein a modulation frequency by an interferometer is set to f , When the repetition frequency of the stimulus is 1 / τ, m / 2τ <f
In a time-resolved Fourier spectroscopy method applied when a detector output signal exists only at <(m + 1) / 2τ (m is a positive integer), a pulse light source has a constant period after the stimulus at the same period as the stimulus repetition period. Light is emitted at a delay time, frequency components in the range of f <1 / 2τ of the obtained detector output signal are extracted, and phase correction is performed to obtain an interferogram for a delay time from the stimulus. It is a method.

[0010]

In each of the first method and the second method, the modulation frequency of the interferometer is f, and the repetition frequency of the stimulus is 1 /.
When τ is set, it can be applied to the case where the detector output signal exists only in m / 2τ <f <(m + 1) / 2τ (m is a positive integer). Time-resolved Fourier spectrometry can be applied to a measurement longer than the reciprocal of twice the maximum frequency f _max , that is, to a measurement target whose response cycle to a stimulus is longer than a sample that was conventionally applicable. . Moreover, by performing a Fourier transform on the interferogram having a lower frequency than the modulation frequency range of the interferometer, the spectrum state in the reaction process of the measurement target can be measured, so that the calculation becomes easier.
In addition, compared with the conventional method, the phase correction of the interferogram is simply performed without changing the configuration of the measuring device, and
The method of the present invention can be easily performed only by performing wave number conversion of the spectrum obtained as a result of the Fourier transform.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in the time-resolved Fourier spectroscopic measurement method proposed by the present applicant, the modulation frequency f of each time-resolved signal of the spectrometer is determined by the repetition frequency 1 / τ (τ: (Repetition period) has been dealt with only in the range smaller than half. On the other hand, according to the present invention, m / 2τ <f <(m + 1) / 2τ
The case where a signal exists only in the range (m is a positive integer) is handled.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration of a time-resolved Fourier spectrometer for implementing one embodiment of the time-resolved Fourier spectrometer according to the present invention. In FIG. 1, 1 is a light source, 2 is an interferometer, and 3 is a sample (in this case, the sample 3 changes its transmittance by stimulation, but may change its reflectance or the like). Reference numeral 4 denotes a stimulus generator, 5 denotes a pulse signal delay circuit, 6 denotes a detector, 7 denotes a preamplifier, 8 denotes a gate circuit, 9 denotes a low-pass filter, 10 denotes a main amplifier, 11 denotes an AD converter, and 12 denotes a computer. The stimulus generator 4 generates a stimulus (trigger) having a constant period τ asynchronously with a reference signal (a sampling signal for A / D-converting an interferogram and taking it into a computer and performing Fourier transform) of the interferometer 2. The delay circuit 5 controls the gate circuit 8 by generating a trigger delayed by a predetermined time Δτ from the synchronization signal of the stimulus generator 4. The gate circuit 8 cuts out the output from the detector 6 at a time delayed by a predetermined time Δτ from the stimulus.
Like the A / D converter 11, the A / D converter has a gate width sufficiently narrow with respect to the period τ, and obtains a comb-shaped interferogram (digital interferogram) by passing a signal only during that period. The low-pass filter 9 is
The low-frequency component of the spectrum obtained from the output of the gate circuit 8 (as described below, f <1 / 2τ) is extracted, and
The signal is converted into an analog signal (analog interferogram) having a spectrum at a fixed delay time Δτ from the stimulation of the sample 3.

Sample 3 used in the system of the present invention
Is a measurement object whose response repeatedly shows the same response to the stimulus.

Therefore, the light source 1, the interferometer 2, the sample 3,
The output from the detector 6 of the FT-IR / spectrometer unit including the detector 6 and the preamplifier 7 is input to the main amplifier 10 of the FT-IR / signal processing unit via the gate circuit 8 and the low-pass filter 9, The data is sampled by the converter 11 for Fourier transform. The stimulus generator 4 outputs a stimulus signal of the sample 3 and a pulse signal synchronized with the stimulus signal. The pulse signal is input to the gate circuit 8 as a trigger via the pulse signal delay circuit 5. Sample 3 is F
Set in the sample chamber of the T-IR / spectrometer section,
The stimulus signal from the stimulus generator 4 is repeatedly stimulated at a period τ. The period τ of this stimulus is generally longer than the reaction period τ ′ from the start of the transient phenomenon of the sample 3 due to the stimulus to its complete decay, and the time width of the stimulus is such that the transient phenomenon starts simultaneously with the stimulus. Must be narrower than the decomposition time to measure the transient. Assuming that the minimum and maximum of the frequency (frequency of the interferogram) in which the spectrum at each decomposition time of the transient is modulated by the interferometer are fmin and fmax, τ> m / 2fmin (a) τ <(m + 1) / 2fmax (b) is repeated at a period τ that satisfies the condition: Here, m is a positive integer. That is, the spectrum from sample 3 is m
/ 2τ <f <(m + 1) / 2τ. FIG. 2A shows a case where m = 1. The modulation frequency f is represented by f = 2vσ, where σ is the wave number of the spectrum (1 / λ when the wavelength is λ), and v is the moving speed of the movable mirror of the interferometer 2, so that the above condition is satisfied. As described above, the emission spectrum region (wavelength range) from the light source 1 may be limited by an optical filter, or the moving speed of the movable mirror may be adjusted to satisfy the above condition. One of the features of this spectrometry is that as can be seen from the conditions described above, the repetition frequency 1 / τ
It is not necessary to synchronize with the movement of the movable mirror.

Now, the principle of spectral separation using the apparatus having such a configuration will be described below. Stimulated sample 3
Is excited with a certain probability, and at the same time begins to decay back to its original state. At this time, the sample 3 absorbs light having a wavenumber of a characteristic band corresponding to the molecular structure in the transient state. The transmittance spectrum (FIG. 3B) of the sample 3 in the transient state due to the single stimulus as shown in FIG. 3A is expressed by T (σ, t) = T ₀ (σ) + T ₁ (σ, t). (1) In the case of a repetitive stimulus as shown in FIG. 3C, T (σ, t) = T ₀ (σ) + T ₁ (σ, t) * Шτ (t) · .. (2) (FIG. 3D). T ₀ (σ) is the transmittance spectrum that is independent of the stimulus, T ₁ (σ, t) is the transmittance spectrum that changes with the stimulus, and Шτ (t) is the time interval τ where the Delak function δ (t) is equally spaced Com function that represents the repetition operation, and *
Is a convolution operation. At this time, the detector 6
The output signal F (x, t) from is given by equation (3). F (x, t) = ∫T (σ, t) B (σ) cos2πx σ dσ = F ₀ (x) + ∫ ｛T ₁ (σ, t) * Шτ (t)｝ B (σ) cos2 πx σ dσ · (3) F ₀ (x) = ∫T ₀ (σ) B (σ) cos2πx σ dσ (3 ′) where F ₀ (x) is the interferometer output of a spectral component unrelated to the stimulus. Where t is the time associated with the sample stimulation, x is the optical path difference of the interferometer 2, σ is the wave number of the spectrum, and B (σ)
Is sample 3 from the sample chamber of the FT-IR / spectrometer section.
Represents a background spectrum when is removed. FIG. 3E shows an approximate state of the output signal of the interferometer with a solid line. Note that x has a relationship of x = 2vt 'with the time variable t', but since the excitation of the sample 3 is not synchronized with the movement of the movable mirror of the interferometer 2, t and t 'are in phase. Has no correlation. That is, the phase amount Δt = t′− between t and t ′
t takes a different value each time the movable mirror scans. For this reason,
The second term in equation (3) indicates that the interferogram shows a different value each time the movable mirror scans.

The output from the detector 6 is supplied to a gate circuit 8
And the time Δτ from the stimulus signal from the stimulus generator 4
It is cut out by the delayed gate signal. This timing is shown in FIG. Here, the time width of the gate signal is narrower than the decomposition time to be measured, but for simplicity, the time width is infinitely small and the sampling process is represented by Шτ (t). At this time, the output signal F '(x, t) from the gate circuit 8 is represented by the equations (4a) and (4b). FIG. 3G shows the state of this signal.

F ′ (x, t) = Шτ (t−Δτ) [F ₀ (x) + ∫ ｛T ₁ (σ, t) * Шτ (t)｝ × B (σ) cos2 πx σ dσ] ( 4a) = Шτ (t-ττ) ∫ T (σ, Bτ) B (σ) cos2 πx σ dσ (4b) The derivation of equation (4a) into equation (4b) will be described later.
The integral part of equation (4b) is the time Δ since the sample 3 was stimulated.
Measurement target spectrum T in the transient state of sample 3 after τ
(σ, Δτ) B (σ) is an interferogram (analog interferogram), and the entire equation (4b) is a discrete data (digital interface) in which this analog signal is sampled at Шτ (t−Δτ). Program). That is, equation (4b) indicates that the measurement signal is time-resolved by this delay time. Since the variables t and x are asynchronous in the sampling, the position where the interferogram is sampled is different each time the movable mirror scans.

In order to know the output from the gate circuit 8 in detail, Шτ (t−Δτ) in the equation (4b) is Fourier-transformed at a time t ′ correlated with the movement of the movable mirror, and the spectrum of the signal is obtained. Find out.

∫Шτ (t−Δτ) exp (−i2πft ′) dt ′ = (1 / τ) exp ｛−i2π (Δτ + Δt) f｝ × Ш1 / τ (f) (5) = ( 1 / τ) [δ (f) + exp ｛-i2π (Δτ + Δt) / τ｝ δ (f-1 / τ) + ・ ・ ・ ・ + exp ｛i2 π (Δτ + Δt) / τ｝ δ ( f + 1 / τ) +...] (5 ′) Equation (5) is a comb function having a phase term. The spectrum obtained when the Fourier transform of the integral part of equation (4b) is performed with respect to time, except for the coefficient, uses the modulation frequency f as a variable.
(f, Δτ) B (f). Therefore, the entire expression (4b), which is the output signal from the gate circuit 8, is the measurement target spectrum T (f, Δ) obtained from the zero-order term δ (f) of the expression (5 ′).
τ) In addition to B (f), exp ｛-i2
This shows that the spectrum obtained from π (Δτ + Δt) / τ｝ δ (f−1 / τ) or the like appears as a sideband analog signal of the carrier frequency n / τ (n is an integer). Where m
Under the condition of / 2τ <f <(m + 1) / 2τ, the spectra of the sidebands do not overlap. This is shown in FIG.
It is shown in (B). The numbers written in the respective spectra in this figure indicate that they are sidebands of the carrier frequency of the same number.

In the case of the present invention, the output from the gate circuit 8 is passed through a low-pass filter 9 having the characteristic shown in FIG. At this time, the low-pass filter 9 outputs an analog signal (analog interferogram) having a spectral component contributed by the second term (+ 1-order term) of the equation (5 ′). The spectrum contributed by the second term is given by the following (6)
It looks like an expression.

F (x, Δτ) = (1 / τ) exp ｛-i2π (Δτ + Δt) / τ｝ × ∫T ｛1 / (2vτ) -σ, Δτ｝ B ｛1 / (2vτ) -σ ｝ Cos2πx σ dσ · (6) The integral term of the equation (6) is a time Δ after the sample 3 is stimulated.
9 shows an interferogram of a spectrum obtained by folding the spectrum in the transient state of Sample 3 after τ. That is, FIG. 3 sampled by the gate circuit 8
The digital signal as shown in FIG. 3G is restored by the low-pass filter 9 into an analog signal as shown in FIG. By the way, since the expression (6) includes the phase of the function of Δt, the form of the analog signal differs every time the moving mirror scans the interferometer. Therefore, the integration of the measured data is
This must be performed after phase correction is performed for each data. That is, since this phase is restored to the analog signal output from the low-pass filter 9, a general FT-
Similarly to the measurement of the IR, the reference signal having the period τ ₀ of the interferometer 2 for the Fourier transform by the AD converter 11 (FIG. 3)
After sampling in (I)), the computer 12
After performing phase correction in (1), integration is performed as it is in the interferogram, and Fourier transform processing is performed later, or Fourier transformation is performed simultaneously with the phase correction to convert to a spectrum, and then integration is performed. At this time, τ ₀ is the low-pass filter 9
Assuming that the minimum and maximum of the modulation frequency of the interferogram signal output from are represented by f _min and f _max , the conditions of τ ₀ > m / 2f _min and τ ₀ <(m + 1) / 2f _max must be satisfied. Here, m is zero or a positive integer.

From the above, the spectrum T ｛1 / (2vτ)-
Since σ, Δτ｝ B ｛1 / (2vτ) -σ 得 is obtained, for example, the ratio with the background spectrum B ｛1 / (2vτ) -σ｝ separately obtained by ordinary FT-IR spectroscopy measurement is obtained. Then, the transmittance spectrum T ｛1 / (2vτ) -σ, Δτ｝ is obtained. Hereinafter, similarly, the delay time of the pulse signal delay circuit 5 is adjusted to adjust the delay time Δτ of the trigger signal to the gate circuit 8.
, A time-series spectrum at a series of delay times is obtained. In this method, since the wave number of the obtained spectrum is folded or shifted, it is necessary for the computer 12 to perform a process of restoring the wave number (wave number change).

As described above, according to the time-resolved Fourier spectrometry of the present invention, the repetition period of the stimulus is a measurement object longer than the reciprocal of twice the maximum frequency f _max of the interferogram signal, and It is possible to measure a transient phenomenon having a repetition cycle that is asynchronous with the sampling cycle.

Here, from the above equation (4a), (4b)
The derivation to the expression will be described. F ′ (x, t) = Шτ (t−Δτ) [F ₀ (x) + ∫ ｛T ₁ (σ, t) * Шτ (t)｝ × B (σ) cos2 πx σ dσ] (4a) ( Шτ (t-Δτ), which represents the sampling process of equation 4a), is
Since it is a function independent of the variable σ, it can be incorporated into the integration of the second term. Here, Ш dependent on the time variable t
Only τ (t−Δτ) ｛T ₁ (σ, t) * {τ (t)} is extracted and the equation is transformed. Since the comb function can be expressed by the sum of the delta functions, Шτ (t) = Σδ (t-nτ) ・ ・ ・ (A1) Шτ (t -Δτ) ｛T ₁ (σ, t) * Шτ (t) こ の(A1)
Rewrite using the formula. Here, n is an integer.

Шτ (t−Δτ) ｛T ₁ (σ, t) * Шτ (t) ｛Σ = ｛Σδ (t−Δτ−nτ)｝ [∫T ₁ (σ, t−t ′) ｛Σδ (t '- mτ)} dt'] = {Σδ (t- Δτ-nτ)} {ΣT 1 (σ, a t-mτ)} ··· (A2 ) m also an integer. Since the stimulus period τ is longer than the lifetime τ ′ of the transient phenomenon of the sample, T ₁ (σ, t) = 0 when t <0 and t ≧ τ. Therefore, a signal can be obtained only when n = m in the equation (A2). Therefore, equation (A2) can be modified as follows.

｛Σδ (t-Δτ-nτ)｝ ｛ΣT ₁ (σ, t-mτ) Σ ｛= Σ ｛δ (t-Δτ-nτ) T ₁ (σ, t-nτ) Σ ｛= Σ ｛δ (t- Δτ-nτ) T ₁ (σ, Δτ)｝ ... (A3) Since T ₁ (σ, Δτ) is a constant and can be rounded down, = T ₁ (σ, Δτ) Σδ (t- Δτ −nτ) = T ₁ (σ, Δτ) Шτ (t−Δτ) (A4) Therefore, T (σ, t) = T ₀ (σ) + T ₁ (σ, t) ((1)
Using equation (4), F ′ (x, t) in equation (4a) is obtained (4b)
The formula, F ′ (x, t) = Шτ (t−Δτ) ∫T (σ, Δτ) B (σ) cos2 πxσ dσ (4b)

The above method is not limited to the above example, and various modifications are possible. For example, the gate circuit may be replaced by turning on / off the supply voltage to the detector in synchronization with the trigger signal from the stimulus generator. Further, the present invention can be similarly applied to fluorescence spectroscopy and Raman spectroscopy in which a sample is irradiated with a pulsed laser. In the case of fluorescence spectroscopy, a pulse laser 26 is directly applied to the sample 21 as shown in FIG. 5, light from the sample 21 is captured by the detector 23 through the interferometer 22, and the same processing as in the embodiment shown in FIG. I do. In the case of Raman spectroscopy, as shown in FIG. 6, a pulse laser 36 is applied to the sample 31 to stimulate it, the sample 31 stimulated by the light from the continuous wave laser 30 is excited, and the Raman , And are taken in by the detector 33, and the same processing as in the embodiment shown in FIG. 5 is performed.

In the apparatus shown in FIGS. 1, 5, and 6, a plurality of channels including a gate circuit and a low-pass filter are provided in parallel, and the same detection signal is input to each channel to stimulate the sample. By making the delay time Δτ from application to opening of each gate circuit different for each channel, the interferogram at a plurality of different delay times after application of the stimulus can be calculated according to the principle described with reference to FIGS. Simultaneously acquiring and performing sampling, phase correction, etc., and then performing Fourier transform on them, it is also possible to simultaneously measure spectral states at different times in the reaction process of the measurement object showing the same response repeatedly to the stimulus. . FIG. 7 shows an example of the configuration of an apparatus for performing such time-resolved Fourier spectroscopy. The sample 2 is stimulated by a repetitive pulse having a period τ from a stimulus generator 4 that generates a repetitive pulse stimulus as shown in FIG. 3C, and the stimulated light from the sample 2 is converted by a detector 6 into a measurement signal. 1, 5 and 6 (the continuous wave laser 30 is not shown). A signal from the detector 6 is input to a plurality of gate circuits 81, 82, 83,. on the other hand,
The repetition signal from the stimulus generator 4 is input to a plurality of delay circuits 51, 52, 53,. The delay circuits 51, 52, 53,... Have different delay times Δτ1,
.DELTA..tau.2, .DELTA..tau.3,...
, Δτ2, Δτ3... After each gate circuit 81, 82, 8
Trigger signal is sent to 3 ... Therefore, from each of the gate circuits 81, 82, 83,..., A comb-shaped interferogram is obtained in which Δτ in FIG. 3F is replaced with Δτ1, Δτ2, Δτ3,. These are, respectively, the delay time Δ
.. is a comb-shaped interferogram obtained by sampling only the signals of τ1, Δτ2, Δτ3,.
Low-pass filters 91, 9 connected to 82, 83,.
2, 93,..., Each comb-shaped interferogram is converted into an analog interferogram as shown in FIG. Then, the AD converter 111, 112, 113 ... provided each interferogram in the same manner as FIG. 1 in each channel are sampled in the digital signal with a period tau ₀ of the reference signal of the interferometer, the computer 12 .., .Tau.2, .DELTA..tau.3, and the spectra representing the state of the sample 3 at the respective delay times .DELTA..tau.1, .DELTA..tau.2, .DELTA..tau.3.
Therefore, the measurement time can be shortened as compared with the methods of FIGS. 1, 5, and 6. As for the method of simultaneously obtaining the spectra at a plurality of different delay times, similarly to the case of Japanese Patent Application No. 2-259355, various other modifications and applications are possible, and refer to the specification.

In the above description, a light source that continuously emits light is used as a light source to observe the transient state at the delay time Δτ after the stimulus is applied, and the output of the detector at this delay time is cut out in a comb shape by the gate circuit. Although the case of outputting a digital interferogram has been described, the method of the present invention uses a pulse light source as a light source, emits light from the stimulus with a delay time Δτ from the stimulus at the same cycle as the stimulus repetition cycle, The present invention can also be applied to a device that outputs a digital interferogram in a transient state from a detector. FIG. 8 shows the configuration of the apparatus in such a case. The pulse light source 13, the interferometer 2, the sample 3, the detector 6, the timer 15, the delay circuit 16, the light source power supply 17, the stimulus generator 4, the preamplifier 7 , The low-pass filter 9, the main amplifier 10, the AD converter 11, and the computer 12 are connected as shown in the figure, and instead of using the gate circuit to cut out the transient state after Δτ after applying the stimulus to the sample 3, as shown in FIG. By exciting the pulse light source 13 after Δτ after applying the stimulus to the sample 3, the same operation as in the case of FIG. 1 is performed. In this example, a pulse light source is provided to stimulate the sample and emit pulse light delayed by a certain time. However, without such a pulse light source, a Raman excitation pulse is provided as shown in FIG. The laser 18 may be used to excite the sample. That is, when this method is applied to a time-resolved FT-Raman apparatus, a Raman excitation pulse laser 18 is used instead of the light source power supply shown in FIG. 8 as shown in FIG. A stimulus is given from the stimulus generator 4 at a period τ, and a trigger delayed by a certain time Δτ from the synchronization signal is generated by the delay circuit 16, and the Raman excitation pulse laser
May be controlled.

Also when such a pulsed light source is used, a plurality of channels composed of a low-pass filter or the like are provided in parallel, the same detection signal is input to each channel, and after the stimulus is applied to the sample and the pulsed light source is excited. By making the delay time Δτ of each channel different for each channel, it is possible to simultaneously measure spectral states at different times in a reaction process of a measurement object that repeatedly shows the same response to a stimulus. FIG. 10 shows a configuration 1 of the apparatus for that purpose.
Here is an example. In this case, the clock signal generated by the timer 15 includes a plurality of delay circuits 61, 62, 6 arranged in parallel.
3 and delay time Δτ1, Δτ2 from stimulus generation
, Δτ3... A trigger signal is sent later. Each delay circuit 61,
The trigger signals from 62, 63...
After the stimulus is applied to the sample 3, a trigger is applied to the light source power source 17 after delay times Δτ1, Δτ2, Δτ3..., And the pulse light source 1 is driven by the trigger. For this reason, for a repetitive stimulus, it is the same as sampling only a detection signal when a gate is applied with a delay time of Δτ1, Δτ2, Δτ3..., And a comb-shaped interferogram is obtained. The comb-like signal is input to the distributor 41 via the preamplifier 7, and the comb-like signal from the detector 4 is connected to the low-pass filter connected to the next stage according to the delay time Δτ1, Δτ2, Δτ3. 91, 92, 93... Thereafter, similarly to FIG. 7, each of the delay times Δτ1, Δτ2, Δτ3.
At the same time is obtained simultaneously. Therefore, also in this case, the measurement time can be shortened as compared with the methods shown in FIGS. As to the method for simultaneously obtaining the spectra at a plurality of different delay times, similarly to the case of Japanese Patent Application No. 2-259356, various other modifications and applications are possible, and refer to the specification.

As a modification of the above embodiment, instead of the low-pass filter, a band-pass filter having a frequency response characteristic for extracting the first-order or higher-order spectral components shown in FIG. It is also possible to extract only

[0033]

As described above, in both the first method using the gate circuit and the second method using the pulse light source, the modulation frequency by the interferometer is f and the repetition frequency of the stimulus is 1 / τ. Then, m / 2τ <f <(m + 1)
/ 2τ (m is a positive integer) can be applied to the case where the detector output signal exists only. Therefore, the time-resolved Fourier spectroscopic measurement is performed on the measurement object whose response cycle to the stimulus is longer than the sample that can be applied conventionally. The law becomes applicable. Moreover, by performing a Fourier transform on the interferogram having a lower frequency than the modulation frequency range of the interferometer, the spectrum state in the reaction process of the measurement target can be measured, so that the calculation becomes easier.
In addition, compared with the conventional method, the phase correction of the interferogram is simply performed without changing the configuration of the measuring device, and
The method of the present invention can be easily performed only by performing wave number conversion of the spectrum obtained as a result of the Fourier transform.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of a time-resolved Fourier spectrometer for performing a first time-resolved Fourier spectrometer according to the present invention.

FIG. 2 is a diagram for explaining an analog interferogram and a digital interferogram and spectra included therein;

FIG. 3 is a waveform chart for explaining the operation of the time-resolved Fourier spectrometry according to the present invention.

4 is a diagram showing a frequency response characteristic of a low-pass filter used in the device of FIG. 1 and an output spectrum thereof.

FIG. 5 is a diagram showing a main part of the configuration of an example in which the first time-resolved Fourier spectrometry of the present invention is applied to fluorescence spectroscopy.

FIG. 6 is a diagram showing a main part of a configuration of an embodiment in which the first time-resolved Fourier spectrometry of the present invention is applied to Raman spectroscopy.

FIG. 7 is a diagram showing a configuration of an embodiment in a case where the first time-resolved Fourier spectrometry of the present invention is performed in multiple channels.

FIG. 8 is a diagram showing a basic configuration of a time-resolved Fourier spectrometer for performing a second time-resolved Fourier spectrometer according to the present invention.

FIG. 9 is a diagram showing a main part of the configuration of an embodiment in which the second time-resolved Fourier spectrometry of the present invention is applied to Raman spectroscopy.

FIG. 10 is a diagram showing a configuration of an embodiment in a case where the second time-resolved Fourier spectrometry of the present invention is performed in multiple channels.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Interferometer 3 ... Sample 4 ... Stimulus generator 5 ... Pulse signal delay circuit 6 ... Detector 7 ... Preamplifier 8 ... Gate circuit 9 ... Low-pass filter 10 ... Main amplifier 11 ... AD converter 12 ... Computer 13 ... Pulse light source 15 ... Timer 16 ... Delay circuit 17 ... Power supply for light source

Claims (2)

(57) [Claims] 1. A stimulus generating means repeatedly applies a stimulus at a cycle longer than a reaction cycle of a measurement object, acquires an interferogram for a certain delay time from the stimulus from a detector output using a rapid scan interferometer, and performs a Fourier transform. A time-resolved Fourier spectroscopy method for measuring a reaction state of a measurement object that repeatedly shows the same response to a stimulus by obtaining a spectrum, wherein a modulation frequency by an interferometer is f and a repetition frequency of the stimulus is 1 / τ. When m
/ 2τ <f <(m + 1) / 2τ (m is a positive integer) in a time-resolved Fourier spectroscopy method applied when a detector output signal exists only at a certain delay time after the stimulus Time-resolved Fourier spectroscopy, wherein a frequency component in a range of f <1 / 2τ of the sampled signal is extracted, and an interferogram for a delay time from the stimulus is obtained by performing phase correction. Law. 2. A stimulus generating means repeatedly applies a stimulus at a cycle longer than a reaction cycle of a measurement object, acquires an interferogram for a fixed delay time from the stimulus from a detector output using a rapid scan interferometer, and performs a Fourier transform. A time-resolved Fourier spectroscopy method for measuring a reaction state of a measurement object that repeatedly shows the same response to a stimulus by obtaining a spectrum, wherein a modulation frequency by an interferometer is f and a repetition frequency of the stimulus is 1 / τ. When m
/ 2τ <f <(m + 1) / 2τ (m is a positive integer) in a time-resolved Fourier spectroscopy method applied when a detector output signal is present only at a period equal to the stimulation repetition period by a pulse light source. After a certain delay time, light is emitted, and the obtained detector output signal f <1 / 2τ
A time-resolved Fourier spectroscopy method, which obtains an interferogram for a certain delay time from a stimulus by extracting frequency components in the range of and performing phase correction.