JPH02223830A - Raman spectrochemical analyzer - Google Patents

Abstract

PURPOSE:To reduce the influence of reflected light and Rayleigh scattered light which are guided in an optical fiber by arranging a filter spectroscope between a light converging part and the optical fiber. CONSTITUTION:The filter spectroscope 22 consisting of a zero-dispersion double monochromator is provided between the optical fiber and light converging part. Then the reflected light, Rayleigh scattered light, and Raman scattered light from a sample which are converged by the light converging part 10 are diffused spectrally by the spectroscope 22 to remove the reflected light and Rayleigh scattered light and only the Raman scattered light is guided in the optical fiber 14. The scattered light which is guided in the fiber 14 is entered into an additive dispersion type double monochromator 12 through a condenser lens 58 and specific spectrochemical analyzing operation is performed. Consequently, no Raman scattered light characteristic to the optical fiber is generated, so a Raman spectrochemical analysis with high accuracy can be made.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a Raman spectrometer, in particular, to a Raman spectrometer that transmits collected Raman scattered light to a spectroscopic analysis section via an optical fiber. When monochromatic light is applied to a sample and the scattered light is collected with a lens and separated into spectra using a diffraction grating, the components of the scattered light include light with the same wavelength as the incident light, as well as light with different wavelengths.

Scattered light with the same wavelength as the incident light is called Rayleigh scattered light, and scattered light with a different wavelength is called Raman scattered light. Raman scattered light is the combination of the frequency unique to the sample with the frequency of the incident light. It is.

Therefore, by spectroscopically analyzing Raman scattered light,
The components of a sample can be measured.

In the past, Raman spectroscopy was mainly used to analyze the molecular structure and functional groups of organic compounds, but recently it has been applied to various samples such as semiconductors, catalysts, biological samples, and air pollutants. is expected.

With the expansion of the range of applications, Raman spectroscopic analysis is required under various environments.
There is a demand for Raman spectroscopic analysis in the tu state, and in order to meet these expectations, a light condensing section that collects the Raman scattered light from the sample and a spectroscopic analysis section that spectrally analyzes the Raman scattered light are connected to an optical fiber. A Raman spectrometer has been developed that is connected to

Therefore, with such an apparatus, it is possible to bring only the light condensing section close to the sample and obtain Raman spectroscopic analysis results at a position sufficiently separated from the light condensing section.

[Problems to be Solved by the Invention] However, in the conventional Raman spectrometer device using an optical fiber, the Raman scattered light is collected in a condensing section and introduced directly into the optical fiber. Light and Rayleigh scattered light will also be introduced into the optical fiber.

In general, Raman scattered light is 10-6 to 10-1 of reflected light or Rayleigh scattered light! The problem is that the light is twice as weak and extremely difficult to analyze the Raman scattered light from the sample due to the reflected light and Ley scattered light.

That is, the reflected light and Rayleigh scattered light introduced into the optical fiber together with the Raman scattered light from the sample generate Raman scattered light on the optical fiber itself. For this reason, the Raman scattered light peculiar to the optical fiber is strongly emitted, and this becomes a background, making it extremely difficult to measure the Raman scattered light of the sample.

This condition is shown in FIGS. 4 and 5.

That is, FIG. 4 shows an example of a Raman spectrum specific to an optical fiber, and when a Raman spectrum of silicon Si is obtained using a Raman spectrometer in which a light condensing part and a spectroscopic analysis part are connected by such an optical fiber, The result is as shown in FIG.

In FIG. 5, peak I is the Raman scattered light of Si, but significant Raman scattered light caused by the optical fiber can be seen before and after it, making measurement of peak I extremely difficult.

In order to eliminate such Raman scattered light originating from the optical fiber, it is possible to install various filters between the light collection unit and the optical fiber to remove reflected light from the sample and Rayleigh scattered light, but using a filter In this case, the removal rate of Rayleigh scattered light cannot be said to be very good, and moreover, the rise of Raman scattered light from the sample becomes worse, resulting in a problem of deterioration of measurement accuracy.

Furthermore, when performing Raman spectroscopy, the wavelength of the laser light etc. irradiated onto the sample is often changed;
If a filter is used, the filter must be replaced each time the wavelength of the irradiated laser beam is changed, which creates a problem in that the measurement becomes extremely complicated.

The present invention has been made in view of the problems of the prior art described above, and an object thereof is to provide a Raman spectrometer that can reduce the effects of reflected light and Rayleigh scattered light introduced into an optical fiber.

[Means for Solving the Problems] In order to achieve the above object, a Raman spectrometer according to the present invention includes an optical fiber that guides Raman scattered light collected by a light collecting section to a spectroscopic analysis section; The present invention is characterized in that it includes a filter spectrometer disposed between the optical fiber and the condenser to remove reflected light and Rayleigh scattered light.

[Function] Since the Raman spectrometer according to the present invention has the above-described means, the reflected light and Rayleigh scattered light from the sample are separated and removed by the filter spectrometer, and only the Raman scattered light is guided to the optical fiber. Ru.

Furthermore, since the band to be analyzed and sampled with a filter spectrometer can be easily changed, even if the wavelength of the laser light irradiated to the sample is changed, it is possible to appropriately guide only the Raman scattered light to the optical fiber. Can be done.

As described above, according to the Raman spectrometer of the present invention, almost no reflected light from the sample and Rayleigh scattered light enter the optical fiber, and no Raman scattered light unique to the optical fiber is generated. .

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a schematic configuration of a Raman spectrometer according to the present invention.

The Raman spectrometer shown in the figure includes a light condensing section 10, a spectroscopic analysis section 12 consisting of an additive-dispersion double monochromator,
The Raman scattered light collected by the light collecting part 10 is transmitted to the spectroscopic analysis part 12.
and an optical fiber 14 that guides light to.

The Raman scattered light guided by the optical fiber 14 is spectrally analyzed by an additive-dispersive double monochromator 12, and the results are recorded on an XY recorder 18 via a DC amplifier 16.

A characteristic feature of the present invention is that a filter spectrometer is disposed between the tip fiber and the light condensing section, and for this reason, in this embodiment, a filter spectrometer consisting of a zero (0) dispersion type double monochromator is used. 22 are provided.

The reflected light, Ley scattered light, and Raman scattered light from the sample collected by the condenser 10 are separated by a filter spectrometer 22, and the reflected light and Ley scattered light are removed, and only the Raman scattered light is transmitted through the optical fiber. The light will be guided to 14.

FIG. 2 shows the detailed structure of the light condensing section 10 and filter spectrometer 22 of the Raman spectrometer according to this embodiment.

As is clear from the figure, the laser light emitted from the laser light source 30 is irradiated onto the surface of the sample 32, and the reflected light, Rayleigh scattered light, and Raman scattered light from the surface of the sample 32 are collected by the condenser 10. The light is focused by the optical lens 34.

The light focused by the focusing lens 34 enters the zero-dispersion double monochromator 22 through the slit 36.

This zero-dispersion double monochromator has two spectrometers connected in series, but this spectrometer only removes reflected laser light and Rayleigh scattered light, and only performs spectral decomposition in the band of Raman scattered light. will not be carried out.

That is, the light passing through the slit 36 first passes through the concave mirror 3.
8 and becomes parallel light, which reaches the diffraction grating 40.

The diffraction grating 40 is rotated at a certain angle, and the diffracted light reaches a concave mirror 42. Here, the diffraction angle by the diffraction grating 40 varies depending on the wavelength of the light, and the reflected laser light and Rayleigh scattered light having the same wavelength as the laser light emitted from the laser light source 30 and the Raman-shifted Raman scattered light are spectrally separated. be done.

Then, the concave mirror 42 passes through the slit 4 through the mirror 44.
6, and only the Raman scattered light component is transmitted through the slit 46 (first monochrome).

The reflected laser beam and the Lely scattered light are removed by the slit 46, and the light transmitted through the slit 46 is subjected to an action opposite to that of the first monochrome by the mirror 48, the concave mirror 50, the diffraction grating 52, and the concave mirror 54. The light that has passed through the slit 46 (the light that has been spectrally removed from the reflected laser beam or Rayleigh scattered light) is returned to the original undivided light and exits from the slit 54.

The Raman scattered light emitted from the slit 54 is imaged on the end face of the optical fiber 14 by the relay lens 56 and is introduced into the optical fiber 14.

Here, as mentioned above, since the zero-dispersion double monochromator only removes reflected laser light and Rayleigh scattered light and does not perform spectral decomposition of Raman scattered light (that is, the image formed by the slit 54 is and 1
: 1 image), the Raman scattered light emitted from the slit 54 and imaged by the relay lens 56 can be made into an extremely small spot, and the light guiding efficiency to the optical fiber 14 is maintained extremely well.

As shown in FIG. 1, the Raman scattered light guided by the optical fiber 14 enters the additive-dispersive double monochromator 12 via the condenser lens 58, where a predetermined spectroscopic analysis is performed.

In other words, the additive-dispersion double monochromator 12 has two spectrometers connected in series, similar to the zero-dispersion double monochromator, but the spectrometer obtained by the first spectrometer is transmitted to the next spectrometer. It is configured to be more weighted and dispersed.

Therefore, the wavelength band of the Raman dispersion light can be separated with high resolution by the additive-dispersion double monochromator 12, and a detailed Raman spectrum can be obtained.

FIG. 3 shows the Raman spectrum of Si obtained using the Raman spectrometer according to this example, and when compared with the conventional Raman spectrum shown in FIG. 5, the Raman spectrum unique to optical fibers is almost removed,
It is understood that only the Si peak (■) is significantly obtained.

As described above, according to the Raman spectrometer according to the present example, since a double monochromator is used as a filter spectrometer, it is possible to efficiently remove the reflected laser light and Rayleigh scattered light from the sample, and to Even when the wavelength of the irradiated laser beam is changed, the removal band can be easily changed.

Furthermore, since the filter spectrometer is a zero-dispersion type, unlike an additive-dispersion double monochromator, it does not perform spectroscopy of Lillaman scattered light, and it is extremely easy to guide the light to an optical fiber.

The Raman scattered light that has been guided through the optical fiber 14 is spectrally analyzed in detail by an additive-dispersive double monochromator, and extremely accurate and highly accurate Raman spectrum data can be obtained.

In this embodiment, an example was explained in which a double monochromator in which two spectrometers were connected in series was used as a spectroscopic means, but the present invention is not limited to this, and one or three or more spectrometers may be connected in series. It can be anything.

[Effects of the Invention] As explained above, according to the Raman spectrometer according to the present invention, since the filter spectrometer is disposed between the light collecting section and the optical fiber, reflected light other than Raman scattered light or Since almost no Rayleigh scattered light is introduced and no Raman scattered light unique to optical fibers is generated, it is possible to perform Raman spectroscopic analysis with extremely high precision.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the overall configuration of a Raman spectrometer according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the configuration of a filter spectrometer of the device shown in FIG. 1, and FIG. An explanatory diagram of the St Raman spectrum obtained by the apparatus shown in the figure, Figure 4 is an explanatory diagram of the Raman spectrum specific to optical fiber, and Figure 5 is an explanatory diagram of the Raman spectrum of Si when no filter spectrometer is installed. be. (Spectral analysis section) 14... Optical fiber 22... Zero dispersion type double monochromator (filter spectrometer)

Claims (1)

[Claims] (1) In a Raman spectrometer that includes a condensing section that condenses Raman scattered light from a sample and a spectroscopic analysis section that spectrally analyzes the Raman scattered light, the Raman scattered light that is condensed by the condensing section A Raman spectrometer comprising: an optical fiber that guides the light to a spectroscopic analysis section; and a filter spectrometer that is disposed between the optical fiber and the condensing section and removes reflected light from the sample and Rayleigh scattered light. .