JPH0640068B2 - Time-resolved spectrophotometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention repeatedly gives a stimulus to a measurement object in which a stimulus is generated periodically by a stimulus generation means, and samples a detector output using a rapid scan interferometer to stimulate the stimulus. The present invention relates to a time-resolved spectroscopic measurement apparatus for measuring the reaction state of a measurement target that repeatedly shows the same response to a stimulus by acquiring an interferogram for a certain delay time and obtaining a spectrum by Fourier transform.

[Conventional technology]

The requirement to measure the reaction state in the process of periodically stimulating a sample by electricity, laser, or other means, and in the process of returning from the stimulus is, for example, when evaluating the characteristics of liquid crystals or in various other fields. is there. As the measuring method, there is a time-resolved spectroscopy using FT-IR (Fourier transform infrared spectrophotometer). Since this method can measure a wide wave number region with a high SN ratio, it has been conventionally developed and used, but it can be classified into a method using a rapid scan interferometer and a method using a step scan interferometer.

FT-IR uses an interferometer consisting of a semi-transparent mirror, a moving mirror, and a fixed mirror, and obtains an interferogram by moving the moving mirror. The interferogram must have constant characteristics such as sample transmittance. There is a condition that it has to be, and if the characteristics of the sample change, when Fourier transforming it, information that is different from the original information will appear.
Therefore, in time-resolved spectroscopy, the period of the stimulus to be given is required to be longer than the time when the reaction ends, but when giving the periodic stimulus, when the stimulus is given regardless of the movement of the moving mirror, It will be necessary to be consistent. Therefore, conventionally, the stimulus is applied in synchronization with the reference signal of the interferometer.

FIG. 4 is a diagram for explaining a conventional example of time-resolved spectroscopy.

In the case of using the rapid scan interferometer, since the interferogram is taken by applying the stimulus in synchronization with the reference signal of the interferometer as described above, it should be divided into the following three cases depending on the length of the reaction cycle of the target. You can

When the response to the stimulus is very slow, that is, the period τ of the reaction of the object or the change of the state similar thereto is longer than the scan time T of the moving mirror (time to measure the entire interferogram obtained by the interferometer once) (τ>
T) Case When the response to the stimulus is relatively slow, that is, longer than the time interval (sampling interval) t at which each point of the point group forming the interferogram is measured (t
<Τ <T) When the response to the stimulus is very fast, that is, when τ <t For example, in the above case, the reaction period τ of the target is longer than the scan time T of the moving mirror, and therefore, FIG. As shown in (1), if the scanning of the movable mirror is accelerated, the interferogram is obtained at a certain delay of the applied stimulus, and the Fourier transform of the interferogram can be performed to obtain the spectrum of the desired certain state.

However, in that case, the reaction time is short, so
As shown in FIG. 4 (b), a plurality of scans are performed to scan the first interferometer, scan the second interferometer, ...
The measurement is performed by shifting the timing of giving the stimulus by the interval t of the reference signal of the interferometer, and the data of the same delay time is identified and edited to form an interferogram to extract a spectrum in a certain state.

Then, in the case of, since the reaction period τ is included in the sampling period t, as shown in FIG. 4 (c), repetitive stimulation is given in synchronization with the reference signal of the interferometer, and with a constant delay time Δτ. A spectrum of a certain state is taken out by making a measurement and editing the data of the same delay time to make an interferogram.

[Problems to be Solved by the Invention]

However, especially in the above case, it is necessary to synchronize with the reference signal of the interferometer and to perform very fast measurement. For example, if an attempt is made to measure 100 points with a sampling cycle t of 100 μS, the measurement will be repeated in a time of 1 μS, and a very large amount of data must be captured and processed in one scan of the moving mirror. Moreover, it is necessary to identify each data after the measurement and edit the data having the same delay time. Then, as FT-IR, high-speed sampling mechanism, data editing function, etc.
It becomes necessary to add functions that were not previously provided.

Further, when the reaction cycle is shorter than the sampling time, a dead time is generated until the next sampling after the reaction is completed, and the measurement efficiency is deteriorated.

Furthermore, in the case of the above example, the stimulus is given in synchronization with the reference signal of the interferometer, but it is difficult to achieve such synchronization, and in the case where a periodic stimulus is naturally excited. Has a problem that it cannot be measured by the above method.

The present invention is to solve the above problems, and an object of the present invention is to provide a special resolution spectroscopic measurement device capable of measuring a sample having a fast reaction cycle of an object asynchronously with a reference signal of an interferometer. .

[Means for Solving the Problems]

Therefore, the present invention, by repeatedly generating a stimulus by the stimulus generating means to the measurement object repeatedly, sampling the detector output using a rapid scan interferometer to obtain an interferogram for a certain delay time from the stimulus, A time-resolved spectroscopic measurement device for measuring a reaction state of a measurement object that repeatedly shows the same response to a stimulus by obtaining a spectrum by Fourier transform, and a gate circuit for gated a detector output, which is connected to the gate means. Equipped with a low-pass filter and a delay unit that controls the gate circuit by delaying for a predetermined time in synchronization with the stimulus, the stimulus is generated asynchronously with the reference signal of the interferometer, and the detector output is sampled after delaying the delay time to be measured. It is characterized in that it is configured to.

[Action]

The time-resolved spectroscopic spectroscope of the present invention includes a gate circuit that gates the detector output, a low-pass filter connected to the gate means, and a delay means that delays a predetermined time in synchronization with the stimulus to control the gate circuit. A stimulus is generated asynchronously with the reference signal of the meter, and the detector output is sampled with a delay time to be measured, so an interferogram for a certain delay time can be obtained and a spectrum can be obtained by Fourier transform. A series of time-series spectra for different delay times can be obtained by changing delay times one after another and performing the same measurement.
Moreover, since there is no restriction on the stimulus generator, it is possible to increase the frequency of the stimulus and measure the fast reaction regardless of the reference signal of the interferometer, even for fast reaction. Further, even in the conventional apparatus using the rapid scan interferometer, it can be realized by adding a simple means without significantly changing the system.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an embodiment of the time-resolved spectroscopic measurement device according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the time-resolved spectroscopic measurement device according to the present invention.

In FIG. 1, 1 is a light source, 2 is an interferometer, 3 is a sample, and 4
Is a 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, 11 is an AD converter, 12 is a CPU
Indicates. The stimulus generator 4 includes an interferometer 2 as shown in FIG.
The stimulus (trigger) (b) having a constant period t'is generated asynchronously with the reference signal (a) of the variable delay circuit 5
Is to control the gate circuit 8 by generating a trigger delayed from the synchronization signal of the stimulus generator 4 by Δτ ′. The gate circuit 8 has a sufficiently narrow gate width with respect to the cycle t ', like the AD converter. By passing a signal only during that period, a comb-shaped signal as shown in FIG. obtain. That is, the repetitive signal is gated 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 system of the present invention is a measurement object in which the reaction repeatedly shows the same response to the stimulus, and the reaction cycle τ of the object is shorter than the sampling interval t at each point of the interferogram.

According to the above 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 applied to the sample 3, a constant delay Δ
Since the output of the detector 6 when it is gated by τ ′ is sampled at equal intervals, it includes a comb function III _t in which the delta function is equally spaced, and F ′ (x) = ∫B ′ (σ, Δτ ′ ) III _{t ′} (t−Δτ ′) (1 + cos2πσx) dσ (2) Here, if the speed of the moving mirror of the interferometer is v,
Although x = 2vt, there is no phase relationship because the stimulus periodically given is asynchronous with the movement with the moving mirror. In (1 + cos2πσx) of the equation (2), only the term with cos2πσx can be converted into a spectrum. Therefore, if only this term is extracted, the output is F ″ (x) = III _{t ′} (t−Δτ ′) ∫B ′ (σ, Δτ ′) cos2πσ × dσ Therefore, in order to see the output obtained when this signal is passed through the low-pass filter 9, III _{t ′} (t−Δτ ′) is Fourier-transformed by t. , And also becomes a comb function. Moreover, it appears at the reciprocal interval of the sampled interval. Therefore, when passing through the low-pass filter 9, F (x) = 1 / t′∫B ′ (σ, Δτ ′) cos2πσxdσ (4), which is obtained as an output. Comparing this expression (4) with the above expression (1), it is shown that the expression F ″ (x) gives an interferogram of the state of the sample when delayed by Δτ ′ after the stimulation is given. Therefore, AD conversion may be performed at a sampling interval determined by the wave number band of the signal.

The present invention is not limited to the above embodiment, and various modifications can be made. For example, the function of the gate circuit itself may be performed by the AD converter. In this case, since the phase is different for each scan of the movable mirror, the interferogram for each scan is phase-corrected by FT to obtain a spectrum and then integrated. Further, the gate circuit may be replaced by turning on / off the voltage supplied to the detector in synchronization with the trigger signal from the stimulus generator. Furthermore, FT Raman (τ ′ =) that irradiates the sample with the pulsed laser
0) and FT Hotorumi can be similarly applied.
In this case, as shown in FIG. 3, the pulse laser 26 is directly applied to the sample 21, the light from the sample 21 is taken in by the detector 23 through the interferometer 22, and the same processing as that of the embodiment shown in FIG. 1 is performed. I do. Further, in the former case, since τ ′ = 0, the gate circuit 25 and the delay circuit 27 may be omitted and the low-pass filter may be directly connected to the preamplifier 24, or the delay circuit may be provided so that substantially equivalent signal processing can be performed. 27 may be set.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the stimulus can be applied asynchronously with the reference signal of the interferometer, so that the constraint on the stimulus can be greatly relaxed. In addition, since the stimulation frequency can be increased for a fast reaction, 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 device with a popularized rapid scan interferometer, the data sampling circuit, data editing software, etc. can be drastically changed. Can be implemented without the need for.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the time-resolved spectroscopic measurement device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the time-resolved spectroscopic measurement device according to the present invention, and FIG. FIG. 4 is a diagram showing another embodiment of the invention, and FIG. 4 is a diagram for explaining a conventional example of a time-resolved spectroscopic device. 1 ... Light source, 2 ... Interferometer, 3 ... Sample, 4 ... Stimulator, 5 ... Variable delay circuit, 6 ... Detector, 7 ... Preamplifier, 8 ... Gate circuit, 9 ... … Low-pass filter, 10 …… Main amplifier, 11 …… AD converter, 12
... CPU.

Claims (2)

[Claims] 1. A stimulus generation unit periodically generates a stimulus and repeatedly applies it to a measurement target, samples a detector output using a rapid scan interferometer to obtain an interferogram for a certain delay time from the stimulus, and Fourier A time-resolved spectroscopic measurement device for measuring a reaction state of a measurement object that repeatedly shows the same response to a stimulus by obtaining a spectrum by conversion, and a gate circuit for gated a detector output, which is connected to the gate means. Equipped with a low-pass filter and a delay unit that controls the gate circuit by delaying for a predetermined time in synchronization with the stimulus, the stimulus is generated asynchronously with the reference signal of the interferometer, and the detector output is sampled after delaying the delay time to be measured. A time-resolved spectroscopic measurement device having the above structure. 2. The time-resolved spectroscopic measurement device according to claim 1, wherein a pulsed laser is applied as a stimulus to the measurement target.