JP2006300808A - Raman spectrometry system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Raman spectrometry system capable of sensitively detecting Raman scattering light and analyzing samples even by a simple structure without having to use a beam splitter. <P>SOLUTION: The Raman spectrometry system provided with a detection means for irradiating a laser beam to a sample to be measured and measuring the intensity of Raman scattering light generated from the sample to be measured is provided with both a reflecting mirror provided with a light transmission opening for passing the laser beam for guiding Raman scattering light to the detection means and a scattering light condensing lens for condensing Raman scattering light to the detection means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Raman spectrometer, and more particularly, to a Raman spectrometer that can detect Raman scattered light with high sensitivity even with a simple structure.

In general, a Raman spectroscopic measurement apparatus is known as a measurement apparatus that irradiates a sample with laser light and separates and measures Raman scattered light generated from the sample. Since this Raman scattered light has an energy spectrum reflecting the material and structure of the sample, detailed information such as constituent elements and molecular structure of the sample can be obtained by measuring the Raman scattered light. .
On the other hand, Raman scattered light has a problem that it is difficult to obtain the intensity required for measurement because the intensity ratio of the entire reflected light is very weak, about 1 / 1,000,000.
Further, since a complicated optical system is required, there has been a problem that the optical path length becomes long and the intensity is easily attenuated.

Therefore, in order to detect the Raman scattered light with sufficient intensity, as shown in FIG. 6, Raman spectroscopic measurement including a laser light source 102, a three-dimensional moving table for moving the sample S, and a beam splitter 108 is provided. A multi-color analyzer 105 as a vessel has been proposed. (See Patent Document 1)
More specifically, when the Raman scattered light is detected by the CCD camera 103, the CCD camera 103 is arranged at a position corresponding to the wavelength, so that an interference filter (bandpass filter) or the like that causes the intensity attenuation can be obtained. A multicolor analyzer 105 for a microscope that can measure the intensity for each wavelength without using a wavelength selection means has been proposed.
JP 2002-14043 (Claims, FIG. 1)

However, the multi-color analyzer described in Patent Document 1 has a structure in which the laser beam and the Raman scattered light overlap on the same optical path. Therefore, in order to separate the two, a transflective type as a beam splitter is used. The mirror had to be placed somewhere on its optical path.
That is, the light that has passed through the beam splitter is separated into transmitted light and reflected light, and the intensity thereof has also been halved. As a result, as a method for detecting Raman scattered light with high sensitivity, an advanced optical path design that shortens the optical path length has been required.
On the other hand, when the method of increasing the output of the laser beam that is incident light is used to amplify the intensity of the Raman scattered light, the variation in the laser beam wavelength is also amplified, and the desired measurement accuracy is obtained. There was also a problem that it was difficult.

Accordingly, the inventors of the present invention have made diligent efforts, and instead of using a beam splitter, by using a reflection mirror having a light passage port for allowing laser light to pass therethrough, even with a simple structure, Raman with good sensitivity can be obtained. The present inventors have found that scattered light can be detected and completed the present invention.
That is, an object of the present invention is to provide a Raman spectroscopic measurement apparatus capable of detecting a Raman scattered light with high sensitivity and analyzing a sample without using a beam splitter.

According to the present invention, there is provided a Raman spectroscopic measurement apparatus having a detecting means for irradiating a measurement sample with laser light and measuring the intensity of Raman scattered light generated from the measurement sample, and allows the laser light to pass therethrough. There is provided a Raman spectroscopic measurement device comprising a reflection mirror for guiding the Raman scattered light to the detection means, and a scattered light focusing lens for focusing the Raman scattered light on the detection means. Thus, the above-described problem can be solved.
That is, as a method of guiding Raman scattered light to the detection means, the problem of intensity reduction can be solved and the Raman scattered light can be detected with high sensitivity by using a reflecting mirror having a light passage opening without using a beam splitter. Can do.

Further, in configuring the Raman spectroscopic measurement apparatus of the present invention, it is preferable that the reflection mirror has a flat plate shape and the reflection mirror is inclined with respect to the measurement sample.
With this configuration, it is possible to accurately define the reflection direction of Raman scattered light, and to efficiently detect Raman scattered light by arranging a scattered light focusing lens in the optical path of the Raman scattered light. Can lead to means.

In configuring the Raman spectroscopic measurement apparatus of the present invention, it is preferable to provide a laser beam focusing lens for focusing the laser beam on the measurement sample inside the light passage opening.
With this configuration, the spot diameter of the laser beam can be focused so as to be minimized on the surface of the measurement sample, and the measurement region can be accurately defined.

In configuring the Raman spectroscopic measurement apparatus of the present invention, it is preferable to place the measurement sample on a sample stage for changing the relative position with respect to the reflection mirror.
With this configuration, the measurement region can be changed while the laser optical system is fixed.

In configuring the Raman spectroscopic measurement apparatus of the present invention, when the diameter of the light passage port is t1 (μm) and the wavelength of the laser beam is t2 (μm), (t1 / t2) × 100 (%) Is preferably a value within the range of 80 to 120 (%).
By configuring in this way, the diameter of the light passage opening can be defined to the minimum necessary, and the light passage opening can be arranged without narrowing the effective reflection area of the reflection mirror surface.

In configuring the Raman spectroscopic measurement apparatus of the present invention, it is preferable to provide a laser oscillator for oscillating laser light with a light source or changing means for changing the wavelength.
By comprising in this way, laser beam conditions can be changed suitably according to the aspect of a measurement sample.

In configuring the Raman spectroscopic measurement apparatus of the present invention, it is preferable to include a temperature control means for stabilizing the wavelength of the Raman scattered light.
By comprising in this way, the dispersion | variation in the wavelength of the Raman scattered light resulting from a temperature change can be suppressed, and the energy spectrum of a Raman scattered light can be measured accurately.

In constructing the Raman spectroscopic measurement apparatus of the present invention, it is preferable to provide an optical interference means for causing optical interference of the Raman scattered light.
With this configuration, the intensity of a specific wavelength region in the Raman scattered light can be selectively amplified, and the sensitivity in the detector can be increased.

  Hereinafter, embodiments of the Raman spectroscopic measurement apparatus of the present invention will be specifically described with reference to the drawings as appropriate.

1. Basic Structure FIG. 1 is a block diagram showing a configuration example of a Raman spectroscopic measurement apparatus according to the present invention.
That is, as shown in FIG. 1, the Raman spectroscopic measurement apparatus 10 mounts a laser transmitter 2 as a light source for emitting laser light, a measurement sample 5 as an object to be irradiated with the laser light, and this measurement sample. A sample stage 6 to be reflected, a reflection mirror 8 for reflecting the Raman scattered light generated from the sample in a predetermined direction, a detecting means 1 for detecting the Raman scattered light, and a Raman scattered light to the detecting means 1 It can be composed of a scattered light focusing lens 9 for focusing, a control means 4 for controlling each block in conjunction with each other, and an image display means 3 for displaying the acquired data as an image.

(1) Sample stage The sample stage 6 in the Raman spectroscopic measurement apparatus 10 is a stage on which the measurement sample 5 is placed, and is provided with a moving mechanism that changes the relative position of the laser beam 11 that is incident light.
More specifically, as shown in FIG. 2, a sample stage 6 supported via a piezo element 15 can be obtained. That is, the sample stage 6 can be moved three-dimensionally in a direction corresponding to the expansion and contraction direction of the piezoelectric element by applying a predetermined voltage to the piezoelectric element 15.

(2) Temperature control means The Raman spectroscopic measurement apparatus 10 includes a temperature adjustment unit 12a having a temperature adjustment function using a heater or the like, and an external temperature adjustment unit 12a in order to suppress variations in wavelength of Raman scattered light. The temperature control unit 12b controlled from the temperature control unit 12 can be connected. The connection location can be arbitrarily selected according to the mode. For example, as shown in FIG. 2, the connection location can be attached to a location in the sample stage close to the measurement sample.
In such a configuration, the wavelength of the generated Raman scattered light can be stabilized by controlling the measurement sample 5 to a desired temperature condition.

(3) Detection means The detection means 1 also includes a spectroscopic means 1a for splitting the Raman scattered light 13 emitted from the measurement sample for each wavelength, and the Raman scattered light split by the spectroscopic means 1a for each wavelength. It can be set as the photodetector 1b carrying CCD etc. which can be counted as the number of photons.
The spectroscopic means 1a includes a plurality of mirrors for reflecting incident light and a diffraction grating for obtaining an interference effect described later. That is, by combining a plurality of mirrors, incident Raman scattered light can be accurately separated for each wavelength, and only a specific wavelength can be amplified by the interference effect by the diffraction grating.
Further, by using the detection means 1 including such a photodetector 1b, Raman scattered light having a plurality of wavelengths can be measured simultaneously.

(4) Laser transmitter The laser transmitter 2 includes a laser light source 2a for emitting excitation light having a predetermined wavelength and a power source 2b for applying a voltage to the laser light source 2a.
The laser light source 2a can be selected in accordance with a desired wavelength, but a semiconductor laser is preferably used as a light source that operates stably.
In addition, the wavelength of the excitation light is preferably a wavelength within a predetermined range in the near infrared, and specifically, a wavelength within a wavelength range of 900 nm or more is preferable. Examples of the laser light source that supplies excitation light in such a wavelength range include an Nd: YAG laser having a wavelength of 1064 nm.
Further, the laser transmitter 2 of the present invention includes a changing means for changing the light source or wavelength described above, and easily changes to a desired light source or wavelength without changing the setting of the optical system or the like. be able to.

(5) Reflection mirror As shown in FIG. 1, the reflection mirror is disposed on the optical path of the laser light 11 and includes a light passage opening 7 for allowing the laser light 11 to pass through. The reflection mirror 8 can be reflected and guided to the detection means 1.
That is, by arranging the reflecting mirror 8 so that the optical path of the laser beam 11 and the light passage port 7 coincide with each other, the Raman scattered light 13 is detected without disturbing the path of the laser beam 11 that is incident light. Can be led in the direction of
Further, it is preferable that the reflecting mirror 8 has a flat plate shape and is inclined with respect to the measurement sample.
With this configuration, the Raman scattered light 13 can be focused on the detection means 1 via the scattered light focusing lens 9, and Raman scattered light that is weak light can be efficiently detected. Can do.
Further, the reflecting surface of the reflecting mirror 8 is not particularly limited as long as it reflects light. However, in order to efficiently reflect light, it is preferable to use a reflecting surface covered with a metal such as aluminum.

(6) Light Passing Port Also, as shown in FIG. 1, the light passing port 7 is a hole provided in a part of the reflection mirror 8, and the light passing port 7 and the optical path of the laser beam 11 overlap. As described above, the reflection mirror 8 can be arranged. With this configuration, the reflection mirror 8 can be disposed at a desired position without hindering the path of the laser beam 11 that is incident light.
Further, the light passage port 7 has a value expressed by (t1 / t2) × 100 (%) when the diameter is t1 (μm) and the wavelength of the laser light is t2 (μm). A value in the range of ~ 120% is preferable. With this configuration, it is possible to arrange the laser beam with the minimum necessary diameter with respect to the laser beam to be used. That is, the light passage opening 7 can be arranged without narrowing the effective reflection area on the surface of the reflection mirror 8.
Further, it is preferable to provide a laser beam focusing lens for focusing the laser beam 11 inside the light passage port 7.
With this configuration, the spot diameter when the measurement sample 5 is irradiated with the laser beam 11 can be controlled. That is, Raman scattered light can be generated only from a specific region on the measurement sample 5, and a more detailed analysis can be performed.

(7) Optical Interfering Means It is preferable that an optical interfering means for causing optical interference of the Raman scattered light 13 is provided inside the Raman spectroscopic measurement apparatus of the present invention.
More specifically, a member that causes an interference effect such as a diffraction grating can be provided anywhere on the optical path of the Raman scattered light 13 reflected by the reflecting mirror 8.
That is, with this configuration, a specific wavelength resulting from the diffraction grating interval is selectively amplified in the Raman scattered light 13 which is weak light, and can be detected with high sensitivity by the detection means 1. Further, as another optical interference means, an optical interference method such as Mach-Zehnder interference, Michelson interference, prism interference or the like can be used.

2. Measurement Method Next, a Raman spectroscopy measurement method using the Raman spectrometer of the present invention will be described in detail with reference to the flowchart shown in FIG.
(1) Input of initial conditions First, in S1 of FIG. 3, the initial conditions are set by setting the scanning range of the sample stage 5, setting the scanning step width, setting the wavelength resolution, and the like. Further, the reflection diffraction grating, filter, and slit in the spectroscopic unit 1a are set, the data acquisition time of the photodetector 1b, the temperature of the temperature control unit 12, and the like are set.

(2) Spectrum measurement Next, spectrum measurement is performed. Here, the spectrum measurement means a series of measurements in which the measurement sample is irradiated with laser light and the generated Raman scattered light is detected for each wavelength.
First, the near-infrared pulsed excitation light supplied from the laser transmitter 2 is guided to the measurement sample 5 by the laser beam optical system 17. The laser beam optical system 17 includes a condenser lens 18, a pinhole mask 19, and a collimator lens 20. When the laser beam passes through the laser beam optical system 17, the laser beam optical system 17 becomes a laser beam 11 of a parallel light flux. .
The laser beam 11 further passes through the light passage opening 7 provided in the reflection mirror 8 and becomes focused light to the measurement sample 5 by the laser light focusing lens 7 a provided in the light passage opening 7. Led.

The laser beam 11 collected on the measurement sample 5 is reflected by the measurement sample 5 including scattered light composed of Raman scattered light, Rayleigh scattered light, and the like.
This scattered light is guided to the detection means 1 by the scattered light optical system 21. The scattered light optical system 21 includes a collimator lens 22, a notch filter 23, and a scattered light focusing lens 9, and is converged and guided to the detection means 1.
More specifically, the scattered light is converted into a parallel constraint by the collimator lens 22 and then passes through the notch filter 23. Here, the notch filter 23 can selectively remove only the intense Rayleigh scattered light of the scattered light. The Raman scattered light 13 that is the scattered light that has passed through the notch filter 23 is focused by the scattered light focusing lens 9 and guided to the detecting means 1.

In the detecting means 1, the light is first separated for each wavelength by the spectroscopic means 1a.
As shown in FIG. 1, the spectroscopic unit 1 a includes mirrors 24, 25, 26, and 27 and a reflective diffraction grating 28.
That is, the Raman scattered light 13 guided into the detection means 1 is reflected by the mirrors 24 and 25 and then diffracted by the reflective diffraction grating 28. At this time, by selecting the grating interval of the reflective diffraction grating 28, only scattered light of a predetermined wavelength can be caused to interfere. That is, the reflective diffraction grating 28 can be replaced with a different one by a so-called turret type.
Next, the light reflected by the reflective diffraction grating 28 is reflected by the mirrors 26 and 27 and guided to the detector 1b.
Thus, in the Raman scattered light 13 incident on the detector 1b, the entire region of the dispersed spectral region can be simultaneously measured by the detector 1b. Further, when the scattered light is observed by the detector 1b, photometry can be performed for a short time, and exposure can be performed for a long time such as several tens of minutes.

(3) Setting of the number of wavelengths and the wavelength bandwidth Next, in the step represented by S3 shown in FIG. 3, the number of measurement wavelengths and the measurement wavelength bandwidth can be appropriately set. For example, as shown in FIG. 4, it is possible to set such that a spectrum including a plurality of peaks in the range of λ1 (nm) to λ2 (nm) is received in N (steps).

(4) Sample stage operation Next, in the step represented by S4 shown in FIG. 3, the movement of the measurement sample 5 and the measurement of the spectrum by the sample stage 6 are repeated, whereby the spectrum data for each point on the measurement sample 5 is obtained. Is obtained, and the three-dimensional spectrum data of the measurement sample 5 is mapped.
Further, as shown in FIG. 5, by setting the number of measurement points and the measurement area on the measurement sample 5, the cell interval L and the measurement areas L1 and L2 that are the scanning area and the step width can be set. That is, Raman spectrum measurement as shown in FIG. 4 can be performed for all the cells set here.

(5) Image Processing and Display Finally, in the step represented by S5 shown in FIG. 3, image processing is performed based on the spectrum data obtained from S1 to S4. At this time, the image display means 3 shown in FIG. 1 can display the distribution state and intensity of the wavelength of the scattered light as a two-dimensional image or a three-dimensional image based on the information from the control means 4, Image processing for displaying a region where the scattered light has a specific wavelength on the measurement sample 5 can also be performed.

As described above in detail, according to the present invention, it is possible to detect Raman scattered light with high sensitivity even if it has a simple structure by measuring using a predetermined Raman spectrometer. It became so.
That is, with the Raman spectroscopic measurement apparatus of the present invention, for example, even for minute measurement objects such as toner particles used in copying machines, measurements such as measurement of the amount of magnetic powder added, identification of constituent elements, identification of constituent organic materials can be performed. It becomes possible.
Therefore, even a measurement object for which it is difficult to obtain sufficient reflection intensity can detect Raman scattered light with high sensitivity and measure it with high accuracy.

1 is a schematic block diagram of a Raman spectrometer of the present invention. It is a figure provided in order to demonstrate the operation mechanism of a sample stage. It is the flowchart which showed the measuring method using the Raman spectroscopy measuring apparatus of this invention. It is a Raman spectrum obtained using the Raman spectrometer of the present invention. It is a figure provided in order to demonstrate the relationship between a measurement sample and a measurement area | region. It is the figure which showed the conventional Raman spectroscopy measuring apparatus.

Explanation of symbols

1: detection means, 2: laser transmitter (light source), 3: image display means, 4: control means, 5: measurement sample, 6: sample stage, 7: light passage port, 8: reflection mirror, 9: scattered light Condensing lens, 11: laser light, 12: temperature control means, 13: Raman scattered light, 15: piezo element, 17: laser light optical system, 21: scattered light optical system, 28: diffraction grating

Claims (8)

A Raman spectroscopic measurement device comprising a detecting means for irradiating a measurement sample with laser light and measuring the intensity of Raman scattered light generated from the measurement sample,
A reflection mirror having a light passage opening for allowing the laser light to pass therethrough, and guiding the Raman scattered light to the detection means;
A scattered light focusing lens for focusing the Raman scattered light on the detection means;
A Raman spectroscopic measurement apparatus comprising:   The Raman spectroscopic measurement apparatus according to claim 1, wherein the reflection mirror has a flat plate shape and the reflection mirror is inclined with respect to the measurement sample.   The Raman spectroscopic measurement apparatus according to claim 1, wherein a laser beam focusing lens for focusing the laser beam on the measurement sample is provided inside the light passage opening.   The Raman spectroscopic measurement apparatus according to claim 1, wherein the measurement sample is placed on a sample stage for changing a relative position with respect to the reflection mirror.   When the diameter of the light passage port is t1 (μm) and the wavelength of the laser beam is t2 (μm), a value represented by (t1 / t2) × 100 (%) is 80 to 120 (% The Raman spectroscopic measurement apparatus according to claim 1, wherein the Raman spectroscopic measurement apparatus has a value within a range of   The Raman spectroscopic measurement apparatus according to claim 1, wherein a laser oscillator for oscillating the laser light is provided with a light source or changing means for changing a wavelength.   The Raman spectroscopic measurement apparatus according to claim 1, further comprising temperature control means for stabilizing the wavelength of the Raman scattered light.   The Raman spectroscopic measurement apparatus according to claim 1, further comprising an optical interference unit configured to cause optical interference of the Raman scattered light.

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