JP2003270043A - Spectroscopic method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly accurate, compact, and lightweight spectroscopic apparatus and its a spectroscopic method. <P>SOLUTION: A pumping light obtained by spectrally separating laser light emitted from a laser light source 2, and probe lights L4 and L5 outputted by a pare-wavelength converting device 7 while wavelength-converting laser light L3 emitted from a laser oscillator 2, are used as measuring light. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectroscopic method and spectroscopic device for specifying a substance to be measured.

[0002]

2. Description of the Related Art The means used for identifying substances are mass spectrometry,
Liquid chromatography or spectroscopy (optical measurement) is generally used.

Further, when it is desired to identify an unknown substance in the field, means for recovering the substance to be measured, such as mass spectrometry or liquid chromatography, is to wash the portion where the substance to be measured comes into contact with each measurement. Alternatively, it is necessary to replace it, and it is not suitable especially when it may be a poison. From the viewpoint of safety, non-contact measurement is desirable.

Optical measurement adapted to them is a non-contact measuring means, and is generally a UV / visible absorption spectrophotometer using a photomultiplier or an infrared absorption scan using a thermo-detector. Vector measurement is effective. A Raman spectrum measuring device using a light scattering spectrum (Raman scattered light) is also used.

A Raman spectrum measuring apparatus irradiates a laser beam onto a molecule or an electronic material, collects Raman scattered light generated by this irradiation with a focusing system, and collects the collected Raman scattered light with a detector (spectrometer). ) Is known as a measuring device for identifying the properties of the spectrum.

Usually, the absorption cross section in the infrared region that causes vibrational level excitation is smaller than that of electronic excitation by three digits or more. Therefore, in order to increase the concentration of excited molecules before the Raman spectrum can be measured, a high-intensity light pulse is required. For example, when a carbon dioxide gas laser is used as the light source, the high intensity of the carbon dioxide gas laser is utilized, and the vibrational level of the molecule is excited by using this pulsed carbon dioxide gas laser (laser light for this excitation is referred to as vibrational level excitation light). Yes, the Raman spectrum of SF ₆ and CF ₃ I molecules is observed by using the second harmonic of the pulsed ruby laser as excitation light (Raman measurement light). Also, by this measurement,
We obtain transient information associated with vibrational excitation of molecules.

[0007]

As shown in FIG. 7, which illustrates the principle of measurement, in the measurement of absorption spectrum, light having a continuous spectrum structure is incident on the substance to be measured, which causes From the difference between the spectrum shape and the transmitted spectrum shape, the absorbed wavelength, that is, the energy level of the substance to be measured can be known, and the substance to be measured can be specified. Usually, the successive scan Bae spectrum light source, measurement area required for a particular substance to be measured is ^700cm -l ^~3500cm
Since it covers a wide area of ^-l , a laser cannot be used, and a lamp must be used.

Further, as shown in the explanatory view of the measurement principle in FIG. 8, in the measurement of the light scattering spectrum, the monochromatic light is made incident on the substance to be measured, and the spectrum shape of the light scattered from there The amount of shift from the original wavelength, that is, the energy level of the substance to be measured can be known, and thus the substance to be measured can be specified.

However, all of these measuring methods are non-contact measurement, but since all of them measure a spectrum, a device for wavelength-resolving light and measuring the intensity of the decomposed wavelength ( The use of so-called spectroscopes has become essential. An apparatus having a spectroscope (for example, a terahertz spectroscope) is required to make the entire spectroscopic system large, heavy, complicated in structure, and precise.

The present invention has been made in view of these circumstances, and an object thereof is to provide a highly accurate, compact and lightweight spectroscopic device and a method thereof.

[0011]

According to the means of the present invention, the measuring object is irradiated with the measuring light, and the Raman scattered light from the measuring object is received by the detector to detect the substance to be measured. In the spectroscopic method for specifying, the measurement light is pump light obtained by dispersing laser light emitted from a laser light source, and probe light obtained by outputting laser light emitted from the laser oscillator by a wavelength conversion device. Is a spectroscopic method.

According to the second aspect of the present invention,
The Raman scattered light detected by the detector is collated with prestored data to specify the measurement target, which is a spectroscopic method.

According to the third aspect of the invention,
A laser oscillator, a spectroscopic unit provided on the front side of the optical axis of the laser beam output from the laser oscillator, a wavelength conversion device provided on the front side of one optical axis split by the spectroscopic unit, Condensing means provided in front of the optical axis on the output side of the wavelength conversion device and the other optical axis separated by the spectroscopic means, and the measurement light condensed by this condensing means irradiates the measurement target. A spectroscope having a detector for detecting Raman scattered light generated from the measurement target.

According to the means of the invention of claim 4,
The wavelength conversion device is a spectroscopic device having a temperature controller connected thereto.

According to the means of the invention of claim 5,
The detector is a spectroscopic device characterized by receiving Raman scattered light from the measurement target as transmitted light or reflected light.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a spectroscopic device according to a first embodiment of the present invention. The spectroscopic device 1 is a light source Y
An isolator 3, a wave plate 4 and a dichroic mirror 5 are sequentially arranged in front of the optical axis of the laser beam L1 emitted by the AG laser oscillator 2.

The laser oscillator 2 has a Q switch Nd: YA
In the case of a G laser, this laser light source has, for example, a wavelength of 1064
nm fundamental wave (repetition period 10 Hz, pulse width 7 ns
Is generated. The laser light L1 emitted from the laser oscillator 2 is rotationally adjusted by the wave plate 4, and is separated by the dichroic mirror 5 into the straight light L2 and the reflected light L3. A wavelength conversion device 7 is arranged in front of the optical axis of the straight traveling light L2 via a condenser lens 6, and the wavelength conversion device 7 is provided.
The rectilinear light L3 incident on the light is wavelength-converted into the converted light L4 and the converted light L5.

The wavelength conversion device 7 is an optical parametric oscillator, and comprises two mirrors 8a and 8b and a periodically poled crystal 9, and a temperature-adjustable crystal holder (not shown) holding the periodically poled crystal 9 is held. A temperature controller 11 for controlling the temperature is connected. The temperature controller 11 may be one using the Peltier effect or a heating constant temperature oven, and is controlled by the computer 10. As the periodically poled crystal 9, a Periodically-Poled-
LiNbO ₃ (PPLN) crystal is used.

The converted light L4 and the converted light L5 emitted from the wavelength conversion device 7 have the same optical axis and are reflected by the mirrors 8a and 8b, and the lens 13 via the reflection mirrors 12a and 12b.
Is focused on the measurement target 14. The wavelengths of the converted light L4 and the converted light L5 are tuned according to the temperature of the periodically poled crystal 9 set by the instruction of the temperature controller 11.

FIG. 2 is a graph showing the crystal temperature tuning of the wavelength of the converted light. The crystal temperature of the periodically poled crystal 9 and the converted light L are shown in FIG.
4 shows the relationship with wavelengths of 4 and L5.

FIG. 3 is a graph showing the correspondence between the crystal temperature and the difference energy between the converted lights (L4 and L5). These graphs are measured from substances and are stored in the computer 10 as a database.

The reflected light L3 reflected by the dichroic mirror 5 is reflected by the mirror 16, passes through the wave plate 17, enters the lens 13, and is condensed on the measurement object 14.
The mirrors 12a, 12b, 16 are adjusted such that the optical axis of the laser light L3, the optical axis of the converted light L4, and the optical axis of the converted light L5 are parallel to each other. The wave plate 17 rotates the polarization of the laser light L3 by 45 ± 1 degrees.

Therefore, the laser light (pump light) L4 and the converted light (probe light) L4 and L5 output from the wavelength conversion device 9 are condensed on the object to be measured 14 via the condensing lens 13, and as a result, , Raman scattered light is generated.

A detector 21 is arranged at a position where the Raman scattered light generated in the direction of passing through the object 14 to be measured is received. The detection device 21 includes a polarizer 22 and a lens 2
3 and the detector 24 are arranged, and the lock-in amplifier 25 is connected to the output side of the detector 24 and the chopper 26 is connected to the lock-in amplifier 25.

As a result, as shown in the explanatory view of FIG.
The Raman scattered light that has passed through the measurement target 14 undergoes phase modulation by the polarizer 22, and only the polarization component orthogonal to the polarization of the incident light passes through. The passed light passes through the lens 23 and is received by the detector 24 as the signal light L6. The light received by the detector 24 is converted into an electric signal and is sent to the lock-in amplifier 25. This lock-in amplifier 2
5 refers to the rotation cycle of the chopper 26 to detect the detector 24
Amplifies the electric signal sent from.

The entire spectroscopic device 1 having these configurations is integrally controlled by the computer 10. As shown in FIG. 5, when the measurement target 14 is measured by these controls, first, it is assumed that the measurement target 14 is in the first vibration level in the state where the laser light is not irradiated. This measurement target 1
To the converted light L having the third wavelength from the wavelength conversion device 7.
By irradiating with 4, the measurement object 14 is excited to the second vibration level. Then, by irradiating the measurement object 14 excited to the second vibration level with the converted light L5,
The measurement target 14 is excited to the third vibration level, and Raman scattered light (anti-Stokes light) is emitted when the measurement target 14 transits from the third vibration level to the first vibration level. The detection device 21 mainly detects this anti-Stokes light.

That is, by adjusting the temperature of the periodically poled crystal 9, they excite only a specific energy level E of the measurement object 14 and the presence or absence of the energy level is converted into the phase modulation intensity of the converted lights L4 and L5. It is a spectroscopic method by measuring with.

The computer 10 converts the temperature set value and the temperature sweep speed of the temperature controller 11 and the temperature and the difference energy between the converted light L4 and the converted light L5 emitted from the wavelength conversion device 7, and the detection device 21. The spectrum shape of the measuring object 14 is determined by correlating the electric signals sent from the. The measurement target 14 is specified by comparing it with the spectrum shape of the known substance in the database stored in the computer 10.

For example, the crystal temperature is 250K to 550K.
By sweeping to the converted light L4, as shown in FIG.
The wavelength (above the broken line in the graph) and the wavelength of the converted light L5 (below the broken line in the graph) can be adjusted. Thereby, as shown the graph in FIG. 3, it can sweep a wide energy range of up to 3500 cm ^-l present inside the measurement object 14.

Next, a second embodiment of the present invention will be described. In the first embodiment described above, the Raman scattered light from the measurement target 14 is the transmitted light from the measurement target 14, but in this case, the measurement target 14 may not transmit light as in the solid state. Object and therefore measurement target 1
The substance is specified by measuring the reflected light from No. 4.

FIG. 6 is a block diagram of the spectroscopic device according to the first embodiment of the present invention. It should be noted that the same functional parts as those in FIG.

In this spectroscopic device 1a, a detection device 21a is arranged at a position for receiving the light reflected by the measuring object 14. The detector 21a includes a polarizer 22a, a lens 23a, a detector 24a, a lock-in amplifier 25, and a chopper 26a as its components.
As a result, the detector 24a causes the signal light L reflected from the measurement target 14 and transmitted through the polarizer 22a and the lens 23a.
7 is received, converted into an electric signal, and the lock-in amplifier 25
Send an electrical signal to. The lock-in amplifier 25 amplifies the electric signal sent from the detector 24 with reference to the rotation cycle of the chopper 26.

The spectroscopic device 1a having such a configuration is wholly controlled by the computer 10, and accordingly, when measuring the measuring object 14, first, in a state where no laser light is irradiated, as shown in FIG. Further, it is assumed that the measurement target 14 is in the first vibration level. The measurement object 14 is excited to the second vibration level by irradiating the measurement object 14 with the converted light L4 having the third wavelength from the wavelength conversion device 7. Then, by irradiating the measurement object 14 excited to the second vibration level with the converted light L5, the measurement object 14 is excited to the third vibration level, and the measurement object 14 is excited.
Raman scattered light (anti-Stokes light) is emitted when the transition from the third vibration level to the first vibration level occurs, and the detection device 21
Then, this anti-Stoke light is mainly detected.

The computer 10 converts the temperature set value and temperature sweep speed of the temperature controller 11 and the temperature and the energy difference between the converted lights L4 and L5 emitted from the wavelength converter 7, and sends them from the detector 21a. The spectrum shape of the measurement object 1444 is determined in correspondence with the received electric signals, and compared with the spectrum shape of the known substance in the database stored inside the computer 10, and the measurement object 14 is measured.
Is being identified. Thereby, the same effect as the transmissive type can be obtained even in the reflective type.

As described above, in the spectroscopic method of each of the above-mentioned embodiments, the temperature control of the wavelength conversion device is used for the spectroscopic analysis without using the spectroscope. realizable.

In the above embodiment, the measurement target is not particularly limited. This is because, in principle, the spectroscopic method and spectroscopic device of the present invention can be applied not only to the state of the substance to be measured.

[0038]

According to the present invention, a highly accurate spectroscopic method for identifying a substance and a miniaturized spectroscopic device can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a spectroscopic device according to a first embodiment of the present invention.

FIG. 2 is a graph showing crystal temperature tuning of the wavelength of converted light.

FIG. 3 is a graph showing a correspondence between a crystal temperature and a difference energy of converted light.

FIG. 4 is an explanatory diagram of a detection device.

FIG. 5 is an explanatory diagram of excitation of a specific energy level.

FIG. 6 is a configuration diagram of a spectroscopic device according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a conventional measurement principle.

FIG. 8 is an explanatory diagram of a conventional measurement principle.

[Explanation of symbols]

1 ... Spectroscopic device, 2 ... Laser oscillator, 7 ... Wavelength conversion device,
11 ... Temperature controller, 14 ... Measurement object, 21 ... Detection device

Claims (5)

[Claims] 1. A spectroscopic method for irradiating a measuring object with measuring light and receiving Raman scattered light from the measuring object with a detector to specify a substance to be measured, wherein the measuring light is from a laser light source. A spectroscopic method comprising pump light obtained by dispersing emitted laser light and probe light produced by outputting the laser light emitted from the laser oscillator by a wavelength conversion device. 2. The spectroscopic method according to claim 1, wherein the Raman scattered light detected by the detector is collated with prestored data to identify the measurement target. 3. A laser oscillator, a spectroscopic means provided in front of the optical axis of laser light output from the laser oscillator, and a wavelength provided in front of one optical axis split by the spectroscopic means. A converter, a condensing unit provided in front of the optical axis on the output side of the wavelength converter and the other optical axis separated by the spectroscopic unit, and the measurement light collected by the condensing unit A spectroscope having a detector for detecting Raman scattered light generated from the measurement target by irradiating the measurement target. 4. The spectroscopic apparatus according to claim 3, wherein the wavelength converter is connected to a temperature controller. 5. The spectroscopic apparatus according to claim 3, wherein the detector receives Raman scattered light from the measurement target as transmitted light or reflected light.