JPH0552654A - Excitation wave length sweep type raman spectroscope - Google Patents

Abstract

PURPOSE:To provide a highly sensitive small sized, lightweight, inexpensive Raman spectroscope having high detecting efficiency for Raman scattered light. CONSTITUTION:An excitation wave length sweep type Raman spectroscope is composed of a wave length variable laser beam source 1, a laser beam collecting system 5 to radiate laser beams to a sample 6, a band pass filter 8 to select light having specific wave length among Raman scattered light generated from the sample 6 and a light detecting system 10, and Raman spectrum of the sample 6 is measured by sweeping wave length of the laser beams.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation wavelength swept Raman spectroscope for measuring the Raman spectrum of a sample by sweeping the wavelength of laser light.

[0002]

2. Description of the Related Art Raman spectra, together with infrared absorption spectra, are well known mainly as a molecular vibration spectrum measuring method for substrates, liquids or solids, and are widely used as a method for evaluating substances. Raman scattering shows that when a substance is irradiated with monochromatic light (cold light) of frequency ν ₀ , in addition to strong scattered light (Rayleigh scattering) of the same frequency as the irradiated light,
As shown in Fig. 2, different frequencies (ν ₀ ± ν ₁ , ν
_This is a phenomenon in which light of ₀ ± ν ₂ ) is scattered. The difference between the frequency of irradiation and the frequency of scattered light (ν ₁ , ν ₂ ...)
Mainly corresponds to the frequency of the molecule, so in conventional Raman measuring devices, ν ₀ is fixed and the scattered light is dispersed by a double monochromator or a triple monochromator to obtain a Raman spectrum.

[0003]

In these conventional Raman spectroscopic measuring devices, the amount of light is increased because the light, which is the Raman scattered light, passes through the entrance slit and the exit slit of the spectroscope and reaches the detector. There is a problem that it becomes less and darker, and the light transmittance is also poor, and it is difficult to say that it is possible to detect weak Raman scattered light efficiently. Further, since the spectroscope is heavy and large, it requires a vast space and is expensive. Therefore, it has been desired to develop a highly sensitive Raman spectroscope having higher detection efficiency of Raman scattered light than that of a conventional Raman spectroscope. The present invention has been made in view of such requirements. An object of the present invention is to provide a Raman spectroscopic device which has high detection efficiency of Raman scattered light, high sensitivity, small size, light weight, and low cost.

[0004]

The present invention relates to an excitation wavelength swept Raman spectroscope, which is a wavelength tunable laser light source and a laser for irradiating a sample with laser excitation light. It is characterized by comprising a light condensing system, a bandpass filter for selecting light of a specific wavelength of Raman scattered light generated from a sample, and a photodetection system. In the present invention, the bandpass filter means an optical element that utilizes light coherence and transmits only light of a specific wavelength and has a significantly low transmittance of light of other wavelengths.

[0005]

In the conventional Raman spectroscope, the wavelength of the excitation light is fixed and the scattered light is dispersed to obtain the spectrum.
However, unlike the conventional Raman spectroscope, the excitation wavelength swept Raman spectroscope of the present invention uses a bandpass filter that allows only light of a specific wavelength to pass. Therefore, since the scattered light of a specific wavelength is detected by the bandpass filter, a tunable laser is used as the excitation laser light, and the oscillation wavelength is swept, thereby
Raman spectra can be obtained.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an excitation wavelength sweeping Raman spectroscopic device of the present invention, which includes a variable wavelength laser light source 1, a laser light focusing system 5, a scattered light focusing system 7, a bandpass filter 8, and a light focusing system. System 9, photodetector 10 and signal processing device 1
It consists of 1. A part of the output light of the wavelength tunable laser light source 1 is split by the beam splitter 2 and guided to the laser wavelength meter 3 and the bandpass filter 4. The laser wavelength meter 3 may be used when it is desired to accurately measure the oscillation wavelength of the variable wavelength laser light source. Further, the bandpass filter 4 may be used when the wavelength tunable laser light contains light that provides a background for measurement, and thereby the light that becomes noise is removed.

The laser excitation light from the bandpass filter 4 is condensed by the condensing system 5 and illuminates the sample 6. Thereby, the Raman scattered light is emitted from the sample 6. The scattered light is then condensed by the scattered light condensing system 7 and transmitted through the bandpass filter 8. At this time, the bandpass filter 8 selects and transmits only light having a specific wavelength. The light selected by the bandpass filter is
The light is collected by the light collecting system 9 and reaches the photodetector 10. The signal from the photodetector is processed by the signal processing device 11.

In the above case, the Raman spectrum of the sample can be recorded by recording the signal intensity from the photodetector 10 while sweeping the oscillation wavelength of the output light from the variable wavelength laser light source 1. Also, the Raman shift is
It can be determined from the oscillation wavelength of the output light from the variable wavelength laser light source 1 and the center wavelength of the bandpass filter 8.

The resolution of the Raman spectroscopic device of the present invention is determined by the line width of the laser excitation light and the characteristics of the bandpass filter. Normally, the line width of the laser excitation light can be made sufficiently narrow, so the bandpass A mechanism for exchanging filters may be additionally provided so that various bandpass filters having different characteristics can be used. This makes it possible to change the resolution of the Raman spectroscope. When the wavelength tunable region of the wavelength tunable laser is narrow and a wide region cannot be measured, a mechanism capable of exchanging several kinds of bandpass filters having different center frequencies may be additionally provided. This makes it possible to expand the measurable wavelength range.

[0010]

The excitation wavelength swept Raman spectroscope of the present invention has the following advantages over the conventional Raman spectroscope. Since the bandpass filter is bright and has high transmittance, Raman scattered light can be efficiently detected.
In addition, since it is small, lightweight, and inexpensive, it is possible to manufacture a Raman spectroscopic device that is small, lightweight, and inexpensive. Since there is no entrance slit, Raman scattered light from a wide area can be detected efficiently. Even if the line width of the excitation laser beam is narrowed to increase the resolution, the bandpass filter does not lower the light transmittance as compared with the spectroscope, and thus can be used for measurement when the resolution is high. Since the wavelength of the scattered light to be detected is constant, the optical system such as the light collecting system can be easily designed. Also,
The Raman shift can be accurately determined by measuring the wavelength of the excitation laser light. Since the wavelength of scattered light to be detected is constant, the sensitivity of the detection system does not change. Therefore, by measuring the output of the laser light source, the sensitivity correction of the Raman spectrum can be easily and easily performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an excitation wavelength sweeping Raman spectroscopic device of the present invention.

FIG. 2 is a diagram illustrating a scattering phenomenon of Raman scattered light.

[Explanation of symbols]

1 ... Variable laser light source, 2 ... Beam splitter, 3 ...
Laser wavelength meter, 4 ... Bandpass filter, 5 ... Laser beam focusing system, 6 ... Sample, 7 ... Scattered light focusing system, 8 ... Bandpass filter, 9 ... Focusing system, 10 ... Photodetector, 1
1 ... Signal processing device.

Claims (1)

[Claims] 1. A variable wavelength laser light source, a laser beam focusing system for irradiating a sample with a laser beam, a bandpass filter for selecting a specific wavelength of Raman scattered light generated from the sample, and a photodetection system. An excitation wavelength-swept Raman spectroscope that measures the Raman spectrum of a sample by sweeping the wavelength of laser light.