JP2769570B2 - Raman spectrometer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Raman spectroscopic analyzer, and more particularly to an improvement in a device for guiding condensed Raman scattered light to a spectroscopic analyzer via an optical fiber.

[Prior Art] Monochromatic light having a short wavelength, such as laser light, is applied to a sample, and scattered light is collected by a lens and separated by a diffraction grating. The scattered light has wavelength components in addition to light having the same wavelength as the incident light. Different lights are also included.

The scattered light having the same wavelength as the incident light is referred to as Rayleigh scattered light, the scattered light having a different wavelength is referred to as Raman scattered light, and the Raman scattered light is the frequency of the incident light combined with the inherent frequency of the sample. It is.

Therefore, the components and the like of the sample can be measured by spectrally analyzing the Raman scattered light.

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

As the range of applications expands, Raman spectroscopy in various environments becomes necessary.For example, samples in cryogenic cryostats, samples in vacuum systems, samples in equipment installation, etc.
Raman spectroscopic analysis in a state is required, and as a means to meet such expectations, a light collecting section for collecting Raman scattered light from a sample and a spectral analyzing section for performing spectral analysis of the Raman scattered light are connected by an optical fiber. A connected Raman spectrometer has been developed.

Therefore, according to such an apparatus, it is possible to bring only the light-collecting portion close to the sample and obtain a Raman spectroscopic analysis result at a position that is fully separated from the light-collecting portion.

[Problems to be Solved by the Invention] However, in the conventional Raman spectroscopic analyzer using an optical fiber, since the Raman scattered light is condensed by the condensing section and directly introduced into the optical fiber, the reflection radiated simultaneously from the sample is reflected. Light and Rayleigh scattered light will also be introduced into the optical fiber.

Generally, Raman scattered light is extremely weak light, which is 10 ^-6 to 10 ^-12 times the reflected light or Rayleigh scattered light, and makes the analysis of Raman scattered light from a sample extremely difficult due to the reflected light and Rayleigh scattered light. There was a problem that would.

That is, the reflected light and the 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,
Raman scattered light peculiar to the optical fiber is strongly emitted, and this becomes a background, which makes it difficult to measure the Raman scattered light of the sample significantly.

 This condition is shown in FIGS. 4 and 5.

That is, FIG. 4 shows an example of a Raman spectrum unique to an optical fiber. When a Raman spectrum of silicon Si is obtained using a Raman spectroscopic analyzer in which a condensing unit and a spectroscopic analyzing unit are connected by such an optical fiber, FIG. The result is as shown in FIG.

In FIG. 5, the peak I is the Raman scattered light of Si, and Raman scattered light due to the optical fiber is remarkably observed before and after the peak I, and it is understood that the measurement of the peak I is extremely difficult.

In order to eliminate Raman scattered light derived from such an optical fiber, various filters may be provided between the light-collecting unit and the optical fiber to eliminate reflected light from the sample and Rayleigh scattered light. In this case, the removal rate of the Rayleigh scattered light cannot be said to be very good, and the problem arises that the rise of the Raman scattered light from the sample is deteriorated and the measurement accuracy is deteriorated.

Furthermore, when performing Raman spectroscopy, the wavelength of the laser beam or the like irradiating the sample is often changed, but if a filter is used, the filter must be replaced each time the wavelength of the irradiating laser beam is changed. In addition, there is a problem that the measurement becomes extremely complicated.

An object of the present invention is to provide a Raman spectrometer capable of reducing 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 spectroscopic analyzer according to the present invention comprises: an optical fiber for guiding Raman scattered light collected by a light collecting unit to a spectral analysis unit; And a filter spectroscope disposed between the optical fiber and the light condensing unit for removing reflected light and Rayleigh scattered light.

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

In addition, since the band to be spectrally collected and collected by the filter spectrometer can be easily changed, even when the wavelength of the laser beam applied to the sample is changed, it is necessary to appropriately guide only the Raman scattered light to the optical fiber. Can be.

As described above, according to the Raman spectrometer according to the present invention, the reflected light from the sample and the Rayleigh scattered light are hardly incident on the optical fiber, and the Raman scattered light unique to the optical fiber does not occur.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

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

The Raman spectrometer shown in FIG. 1 includes a condensing unit 10, a spectroscopic analyzing unit 12 including a dispersion type double monochromator, and a light guiding unit for guiding the Raman scattered light collected by the condensing unit 10 to the spectroscopic analyzing unit 12. And an optical fiber 14.

The Raman scattered light guided by the optical fiber 14 is spectrally analyzed by the additive / dispersion type double monochromator 12, and the result is passed through a DC amplifier 16 to an XY recorder 18.
It is recorded in.

A feature of the present invention is that a filter spectroscope is disposed between the optical fiber and the light condensing unit. For this reason, in the present embodiment, the filter spectroscope 22 composed of a zero (0) dispersion type double monochromator is used. Is provided.

The reflected light, the Rayleigh scattering system, and the Raman scattered light from the sample condensed by the light condensing unit 10 are separated by the filter spectroscope 22 so that the reflected light and the Rayleigh scattered light are removed and only the Raman scattered light is transmitted through the optical fiber. It will be guided to 14.

FIG. 2 shows a detailed structure of the light condensing unit 10 and the filter spectroscope 22 of the Raman spectroscopic analyzer according to the present embodiment.

As is clear from the figure, the laser light emitted from the laser light source 30 irradiates 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 focusing unit.
The light is condensed by ten condensing lenses.

The light condensed by the condenser lens 34 enters the zero-dispersion double monochromator 22 via the slit 36.

This zero-dispersion double monochromator is composed of two spectrometers connected in series. This spectrometer only removes reflected laser light and Rayleigh scattered light, and resolves the spectrum in the band of Raman scattered light. Is not performed.

That is, the light that has passed through the slit 36 is first reflected by the concave mirror 38.
Is reflected by the laser beam to become parallel light and reaches the diffraction grating 40.

The diffraction grating 40 rotates at a certain angle, and the diffracted light reaches the concave mirror 42. Here, the diffraction angle by the diffraction grating 40 differs depending on the wavelength of the light, and the reflected laser light and the 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. Is done.

Then, the concave mirror 42 forms an image on the slit 46 via the mirror 44, and transmits only the Raman scattered light component from the slit 46 (first monochrome).

The reflected laser light and the Rayleigh scattered light are removed by the slit 46, and the light transmitted through the slit 46 is reflected by the mirror 48 and the concave mirror 5.
0, the action opposite to that of the first monochrome is performed by the diffraction grating 52 and the concave mirror 54, and the light transmitted through the slit 46 (the light obtained by spectrally removing the reflected laser light or the Rayleigh scattered light) is not separated into the original light. The light is returned to the 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 described above, the zero-dispersion double monochromator only removes reflected laser light and Rayleigh scattered light and does not perform spectral decomposition of Raman scattered light. And 1:
(For 1 image), relay lens 56 emitted from slit 54
The Raman scattered light to be imaged can be formed into an extremely small spot, and the efficiency of guiding the light to the optical fiber 14 can be maintained extremely well.

Then, as shown in FIG. 1, the Raman scattered light guided by the optical fiber 14 enters the addition / dispersion type double monochromator 12 via the condenser lens 58, and a predetermined spectral analysis operation is performed.

That is, the additive-dispersion type double monochromator 12 has two spectrometers connected in series similarly to the zero-dispersion type double monochromator, but the spectrum obtained by the first spectrometer is used by the next spectrometer. It is configured to be more weighted and dispersed.

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

FIG. 3 shows a Raman spectrum of Si obtained by using the Raman spectroscopic analyzer according to the present embodiment. Compared with the conventional Raman spectrum shown in FIG. Removed
It is understood that only the peak I of Si is significantly obtained.

As described above, according to the Raman spectrometer according to the present embodiment, since the double monochromator is used as the filter spectroscope, the reflected laser light and the Rayleigh scattered light from the sample are efficiently removed, and the irradiation laser light is removed. Even when the light wavelength is changed, the removal band can be easily changed.

Further, since the filter spectroscope is of the zero dispersion type, unlike the decomposable double monochromator, it does not separate the Raman scattered light, and it is extremely easy to guide the light to the optical fiber.

Then, the Raman scattered light guided through the optical fiber 14 is dispersed in detail by the additive / dispersion type double monochromator, and extremely accurate and highly accurate Raman spectrum data can be obtained.

In this embodiment, a spectroscope is used as a spectroscope.
Although the example using the double monochromator connected in series has been described, the invention is not limited to this, and one or three or more units may be connected in series.

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

[Brief description of the drawings]

FIG. 1 is an explanatory view of the overall configuration of a Raman spectroscopic analyzer according to one embodiment of the present invention, FIG. 2 is an explanatory view of the configuration of a filter spectroscope of the apparatus shown in FIG. 1, and FIG. FIG. 4 is an explanatory diagram of a Si Raman spectrum obtained by the apparatus shown in the figure, FIG. 4 is an explanatory diagram of a Raman spectrum unique to an optical fiber, and FIG. 5 is an explanatory diagram of a Raman spectrum of Si without a filter spectroscope. . 10: Condenser unit 12: Additive dispersion type monochromator (spectral analysis unit) 14 ... Optical fiber 22: Zero dispersion type monochromator (filter spectrometer)

Claims (1)

(57) [Claims] 1. A Raman spectroscopic analyzer comprising: a condenser for condensing Raman scattered light from a sample; and a spectroscopic analyzer for spectrally analyzing the Raman scattered light. Raman spectroscopy, comprising: an optical fiber that guides scattered light to a spectroscopic analysis unit; and a filter spectroscope that is disposed between the optical fiber and the light collection unit and that removes reflected light from a sample and Rayleigh scattered light. Analysis equipment.