JP2806615B2 - Time-resolved spectroscopy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of generating a stimulus periodically by a stimulus generating means and repeatedly applying the stimulus to a measurement object, and outputting a detector output using a rapid scan interferometer after the stimulus. Time to measure the state of the spectrum in the reaction process of the measurement object that repeatedly shows the same response to the stimulus by separately sampling at different delay times and acquiring the interferogram for each delay time and obtaining the spectrum by Fourier transform. The present invention relates to resolution spectrometry.

[Conventional technology]

In the process of periodically stimulating a sample with electricity, laser, or other means and recovering from the stimulus, the need to measure the state of the reaction is important, for example, when evaluating the properties of liquid crystals or in various other fields. is there. As a measuring method, there is a time-resolved spectroscopic measuring method using FT-IR (Fourier transform infrared spectrophotometer). This method has been conventionally developed and used because it can measure a wide wavenumber range with a high SN ratio. However, it can be classified into a method using a rapid scan interferometer and a method using a step scan interferometer.

The FT-IR uses an interferometer consisting of a semi-transmissive mirror, a movable mirror, and a fixed mirror, and obtains an interferogram by moving the movable mirror.In the interferogram, characteristics such as the transmittance of a sample are constant during measurement. There is a condition that it must be the same, and if the characteristics of the sample are changed, information different from the original information will be output if the sample is Fourier-transformed. Therefore, in time-resolved spectroscopy, the period of the applied stimulus must be longer than the time at which the reaction ends, but when applying a periodic stimulus, applying the stimulus irrespective of the case of a moving mirror, It is necessary to take 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 generated a stimulus periodically by the stimulus generation means and repeatedly applied the stimulus to the object to be measured. From the output of the detector using the rapid scan interferometer, a certain delay time from the stimulus is obtained. A time-resolved spectroscopic method for measuring a reaction state of a measurement object that repeatedly shows the same response to a stimulus by acquiring an interferogram and obtaining a spectrum by Fourier transform, wherein a detector output is set to a fixed value after the stimulus. A time-resolved spectroscopic measurement method characterized by acquiring an interferogram for a certain delay time from a stimulus by sampling at a delay time and obtaining an envelope of the sampled signal has been proposed (Japanese Patent Application No. 1-230209). . This method allows the stimulation to be given asynchronously with the reference signal of the interferometer,
Can greatly reduce the constraints on the stimulus,
For a fast response, the stimulation frequency can be increased,
The measurement efficiency can be improved.Furthermore, by adding a stimulus generator, a variable delay circuit, a gate circuit, and a low-pass filter to a generally-used device having a rapid scan interferometer, a data sampling circuit, It has the merit that it can be implemented without requiring significant changes to the system, such as data editing software.

Hereinafter, this method will be briefly described. FIG. 3 is a diagram showing a configuration of an example of an apparatus for performing the time-resolved spectrometry according to the above proposal, and FIG. 4 is a waveform diagram for explaining the operation. In FIG. 3, 1 is a light source, 2 is an interferometer,
3 is a sample, 4 is a repetitive pulse stimulus generator, 5 is a variable delay circuit, 6 is a detector, 7 is a preamplifier, 8 is a gate circuit, 9 is a low-pass filter, 10 is a main amplifier, and 11 is AD.
The converter 12 indicates a CPU. The stimulus generator 4 generates a stimulus (b) having a constant period t 'asynchronously with the reference signal (a) of the interferometer 2 as shown in FIG. A certain period of time Δ
The gate circuit 8 is controlled by generating a trigger delayed by τ ′. The gate circuit 8 has a gate width which is sufficiently narrow with respect to the period t ', similarly to the AD converter. By passing the signal only during this period, the comb-like signal is formed as shown in FIG. obtain. That is, a gate is applied to the repetitive signal with a certain delay time from the stimulus, and only the signal having a constant delay time with respect to the stimulus is sampled to obtain a comb-shaped interferogram. The low-pass filter 9 is used to remove harmonics obtained from the output of the gate circuit 8 and obtain an envelope of the output of the gate circuit 8. As a result, the comb-shaped interferogram is converted into a normal analog signal.

The sample 3 used in the above system is a measurement target whose response repeatedly shows the same response to the stimulus, and the stimulus cycle t ′ is longer than the target reaction cycle τ.

According to such a configuration, the output of the detector 6 when the sample 3 does not change is: F (x) = ∫B (σ) (1 + cos2πσx) dσ (σ; wave number = 1 / λ) (1) However, when a stimulus is given to the sample 3, a certain delay Δ
tau 'output of the detector 6 when it is gated by Since the sampling at regular intervals, including a comb function S _t where the delta function at regular intervals, F' (x) = ∫B '(σ, Δτ' ) Ш _t (t−Δ
τ ′) × (1 + cos2πσx) dσ (2) Here, assuming that the speed of the moving mirror of the interferometer is v,
Although x = 2vt, there is no phase relationship because the periodically applied stimulus is asynchronous with the movement with the movable mirror. Above in (2) of the (1 + cos2πσx), since only terms are hazy cosπσx can be converted into a spectrum, the extracted only this section, the output is, F "(x) = Ш t (t-Δτ ') × ∫B ′ (σ, Δτ ′) cos2πσxdσ Then, in order to see the output obtained when this signal is passed through the low-pass filter 9, Ш _t (t−Δτ ′) is Fourier-transformed with t. Which is also a comb function. In addition, it is output at an interval that is the reciprocal of the sampling interval. Therefore, when passed through the low-pass filter 9, F (x) = 1 / t'tB '(σ, Δτ') cos2πσxd
σ (4), which is obtained as an output. Comparing this equation (4) with the above equation (1), the equation of F (x) shows that an interferogram of the sample state when delayed by Δτ ′ after applying the stimulus was obtained. . Therefore, AD conversion may be performed at a sampling interval determined by the wave number band of the signal.

Note that this method is not limited to the above example, and various modifications are possible. For example, the function of the gate circuit itself may be performed by an AD converter.
In this case, since the phase is different for each scan of the moving mirror, the interferogram for each scan is phase-collected by Fourier transform to obtain a spectrum and then integrated. Alternatively, the gate circuit may be replaced by turning on / off the supply voltage to the detector in synchronization with a 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.
And the same processing as in the embodiment shown in FIG. 3 is performed. In the case of Raman spectroscopy, as shown in FIG.
The sample 31 stimulated by the light from 30 is excited, the Raman light is captured by the detector 33 through the interferometer 32, and the same processing as in the embodiment shown in FIG. 5 is performed.

[Problems to be solved by the invention]

In the time-resolved spectrometry method proposed by the applicant as described above, the interferogram at a predetermined delay time after applying a stimulus can be measured, but the interferogram at several different delay times can be measured. In order to measure the gram, the same measurement must be repeated by changing the delay time of the delay circuits 5, 27, and 37.
Measurement takes a very long time.

The present invention has been made in view of such a situation, and uses a rapid scan interferometer to simultaneously acquire interferograms at a plurality of different delay times and perform a Fourier transform on the interferograms. An object of the present invention is to provide a time-resolved spectrometry for simultaneously measuring spectral states at different times in a reaction process of a measurement object having the same response.

[Means for solving the problem]

The time-resolved spectroscopic measurement method of the present invention that achieves the above object,
A stimulus is periodically generated by the stimulus generation means and repeatedly applied to a measurement object, and a detector output signal using a rapid scan interferometer is sampled at a fixed delay time after the stimulus, and an envelope of the sampled signal is obtained. In the time-resolved spectroscopy method of obtaining the interferogram for a certain delay time from the stimulus by obtaining and obtaining the spectrum by Fourier transform, the reaction state of the measurement object showing the same response repeatedly to the stimulus is measured.
The same detector output signal is sampled separately at a plurality of different delay times, an interferogram for each delay time is obtained by obtaining an envelope of each sampled signal, and each interferogram is supported by performing a Fourier transform. This method is characterized by simultaneously measuring the response states of a plurality of measurement targets that exhibit the same response to a stimulus repeatedly at a plurality of delay times by obtaining a spectrum of the delay time.

[Action]

In the present invention, the same detector output signal using a rapid scan interferometer is separately sampled at a plurality of different delay times, and an interferogram for each delay time is obtained by obtaining an envelope of each sampled signal. Then, by obtaining a spectrum of the corresponding delay time by performing a Fourier transform on each interferogram, the reaction state at a plurality of delay times of the measurement object that repeatedly shows the same response to the stimulus is simultaneously measured. Therefore, it is not necessary to repeat the same measurement while changing the delay time for the same sample, and transient phenomena at different times when a stimulus is applied to the sample can be simultaneously measured in a short time.

〔Example〕

Next, an embodiment of the time-resolved spectrometry of the present invention will be described with reference to the drawings.

The basic idea of the present invention is that, in the apparatus shown in FIGS. 3, 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. Then, by making the delay time Δτ ′ between applying the stimulus to the sample and opening each gate circuit different for each channel, the stimulus is applied after the stimulus is applied in accordance with the principle described with reference to FIGS. Interferograms at different delay times are simultaneously obtained and Fourier-transformed 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. 1 is a diagram showing a basic configuration of an apparatus for carrying out this time-resolved spectrometry, and FIG.
Is stimulated by a repetitive pulse having a period t ′ from the stimulus generator 4 which generates a repetitive pulse stimulus as shown in FIG.
3, 5 and 6 up to the point where the light from the stimulated sample 2 is converted into a measurement signal by the detector 6 (light source 1, continuous wave laser 30 is shown). Absent.). The signal from the detector 6 is input to a plurality of gate circuits 81, 82, 83,. On the other hand, the repetitive signal from the stimulus generator 4 as shown in FIG. 4 (b) is input to a plurality of delay circuits 51, 52, 53,.
The delay circuits 51, 52, 53,.
1 ', .DELTA..tau.2', .DELTA..tau.3 ',... And each gate circuit after delay time .DELTA..tau.1', .DELTA..tau.2 ', .DELTA..tau.3',.
Trigger signals are sent to 81, 82, 83 ...
Therefore, from each of the gate circuits 81, 82, 83,..., Δτ ′ in FIG. 4 (d) becomes Δτ1 ′, Δτ2 ′, Δτ
The interferogram in the form of a comb which is sampled while being replaced by 3 'is obtained. These are interferograms in the form of combs obtained by sampling only signals of delay times Δτ1 ′, Δτ2 ′, Δτ3 ′... With respect to the stimulus, and are low-pass filters 91 connected to the respective gate circuits 81, 82, 83. , 92, 93... Each of the comb-shaped interferograms is converted into an envelope analog interferogram as shown in FIG. Each interferogram is converted by AD converters 111, 112, 113,... Provided for each channel in the same manner as in FIG.
A digital signal as shown in FIG. 4 (f) is sampled at the period t of the reference signal of the interferometer, taken into the CPU 12 and Fourier-transformed, and each delay time Δτ1 ′, Δτ
2 ′, Δτ3 ′... Are simultaneously obtained. Therefore, the measurement time can be shortened as compared with the previously proposed method.

Next, FIG. 2 shows an apparatus having another configuration for performing the time-resolved spectrometry of the present invention. The difference from the case of FIG. 1 is that instead of using a plurality of delay circuits 51, 52, 53... Corresponding to each channel, a repetitive pulse having a period t 'from a repetitive pulse stimulus generator 4 is used. Multiplied pulse generator 41 for multiplying the multiplied pulse into a repetitive pulse having a period t '/ n (n: an integer of 2 or more), and a phase (delay time) of the multiplied pulse from the multiplied pulse generator 41 from the stimulus to t' / n n,
A pulse distributor 42 for distributing repetitive pulses having a period t 'different by 2t' / n, 3t '/ n... Is used, and the pulses distributed by the pulse distributor 42 are used as trigger signals for each gate circuit.
81, 82, 83... In the case of FIG. 1, the delay time of each channel can be arbitrarily set. In this case, the difference is that the delay time is limited to an integral multiple of t '/ n, but the other operations are the same.

The above examples were for normal IR spectroscopy,
Similarly, it is clear that the method of the present invention can be applied to Raman spectroscopy and fluorescence spectroscopy shown in FIGS.

In addition, various modifications are possible. For example, in the case of FIG. 1, the temporal relationship between the stimulus applied to the sample 3 and the trigger signals applied to the gate circuits 81, 82, 83,... Prepare,
The pulses are sequentially applied to the sample 3 stimulus, the gate circuit 81 trigger, the gate circuit 82 trigger, the gate circuit 83 trigger ..., the sample 3 stimulus, the gate circuit 81 trigger, the gate circuit 82 trigger, the gate circuit 83. For triggering, etc., it may be arranged. Further, one gate circuit is formed, and the delay time Δτ
1 ', Δτ2', Δτ3 '... or t' / n, 2t '/ n, 3t' /
.. may be sampled and the pulse sequence signal may be distributed to the low-pass filters 91, 92, 93,. Also, the signals passed through the low-pass filters 91, 92, 93, ... and the main amplifiers 101, 102, 103, ... can be taken in one AD converter in time series and sampled. The point is that separate low-pass filters 91, 92, 93,... Are provided for each channel, and other modifications are possible. Accordingly, the arrangement of the above devices is for illustration only and is not intended to limit the invention.

〔The invention's effect〕

According to the time-resolved spectrometry of the present invention, each delay is obtained by separately sampling the same detector output signal using a rapid scan interferometer at a plurality of different delay times and obtaining an envelope of each sampled signal. Obtain interferograms with respect to time and obtain the corresponding delay time spectrum by performing Fourier transform on each interferogram, thereby simultaneously measuring the response state of the measurement object that repeatedly shows the same response to the stimulus at multiple delay times It is not necessary to repeat the same measurement by changing the delay time for the same sample, and it is possible to simultaneously measure transient phenomena at different times when a stimulus is applied to the sample in a short time. .

In addition, the method of the present invention can provide a stimulus asynchronously with the reference signal of the interferometer, similarly to the time-resolved spectroscopic method on which the method is based, so that the restriction on the stimulus can be greatly eased. For a fast reaction, the stimulus frequency can be increased, so that the measurement efficiency can be improved.In addition, a stimulus generator, a variable delay circuit, By adding a gate circuit, a low-pass filter, and the like, there is an advantage that the present invention can be implemented without requiring a significant change in the system such as a data sampling circuit and data editing software.

[Brief description of the drawings]

FIG. 1 is a diagram showing the basic configuration of an apparatus for performing the time-resolved spectrometry of the present invention, and FIG. 2 is a diagram showing the configuration of another apparatus for performing the time-resolved spectrometry of the present invention. Figure,
FIG. 3 is a diagram showing the configuration of an apparatus for performing the time-resolved spectrometry based on the premise of the present invention. FIG. 4 is a waveform diagram for explaining the operation of the apparatus shown in FIG. 3, FIG. FIG. 6 is a diagram showing the configuration of another apparatus for performing the time-resolved spectrometry based on the premise of the present invention. 1, light source, 2, 22, 32, interferometer, 3, 21, 31, sample 4, stimulus generator, 5, 27, 37, variable delay circuit, 6, 23, 33 Detector 7, 24, 34 Preamplifier 8, 25, 35 Gate circuit 9, Low-pass filter 10, Main amplifier 11, AD converter 12, CP
U, 26, 36: pulse laser, 30: continuous wave laser, 4
1… Multiplier pulse generator, 42… Pulse distributor, 51, 5
2, 53 ... delay circuit, 81, 82, 83 ... gate circuit, 91, 9
2, 93 ... low-pass filter, 111, 112, 113 ... AD converter

Claims (1)

(57) [Claims] A stimulus generation means periodically generates a stimulus and repeatedly supplies the stimulus to an object to be measured. A detector output signal using a rapid scan interferometer is sampled at a fixed delay time after the stimulus, and the sample is sampled. Time-resolved spectroscopy that obtains the interferogram for a certain delay time from the stimulus by obtaining the signal envelope and obtains the spectrum by Fourier transform, thereby measuring the response state of the measurement object that repeatedly shows the same response to the stimulus In the method, the same detector output signal is sampled separately at a plurality of different delay times, an interferogram for each delay time is obtained by obtaining an envelope of each sampled signal, and a Fourier transform is performed on each interferogram. To obtain the corresponding delay time spectrum. By time-resolved spectroscopic measurement method characterized by simultaneously measuring the reaction conditions in a plurality of delay time to be measured showing the same response repeatedly to stimulation.