JPS58219439A - Spectrochemical analysis device using laser light - Google Patents

Abstract

PURPOSE:To make it possible to set the distance between the surface of a sample and a spectroscope arbitrarily, by providing a condenser lens, ring shaped concave and convex mirrors, and a spectroscope optical system, and making laser light and light from a sample in parallel on the same axis between the concave and convex mirrors and the spectroscope optical system. CONSTITUTION:A condenser lens 32 converges laser light 13 on the surface of a sample. A ring shaped concave mirror 34 and a convex mirror 36 make light 37 emitted from the sample to be a ring shaped parallel light beam, which is propagated in the reverse direction on the same axis. A ring shaped concave mirror 40 guides the light 37 from the sample to a spectroscope 22. A spectroscope optical system 20 includes expandable mirror tubes 46 and 46a. The laser light 13 and the light 37 from the sample are made to be in parallel on the same axis between the ring shaped concave and convex mirrors 34 and 36 and the spectroscope optical system 20. In this constitution, the light 37 from the sample is efficiently guided to a spectroscope 22 by the adjustment of the mirror tubes 46 and 46a, regardless of the length of the distance between the sample 16 and the spectroscope 22. Thus the highly accurate, general purpose device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser emission spectrometer, which is suitable for direct analysis of hot metal, molten steel, and molten slag. The present invention relates to an improvement of a laser emission spectrometer that spectrally analyzes light emitted from a laser beam using a single spectroscope.

When a strong pulsed laser beam is irradiated onto the surface of a sample, energy is locally injected, causing melting and evaporation, and the vapor is further excited to become plasma and emit light. Laser emission spectrometry that determines the content of the target element by dispersing this light with a spectrometer and measuring the spectral line intensity of the target element using photographic film, photomultiplier tubes, photodiodes, etc. The device is known.

As shown in FIG. 1, an optical system used in a laser emission spectrometer using laser light as an excitation source includes a laser emission section 12. A laser irradiation system 10 includes a condenser lens 14 for converging the laser light emitted from the laser emitting unit 12 onto the surface of the sample 16, and a spectroscope 22 for transmitting the light emitted from the surface of the sample 16. As shown in FIG. 2, a spectrometer optical system 20% for guiding and a spectrometer system 18 consisting of five spectrometers 22 are arranged on separate axes, and the sample 16f is installed at the point where they intersect. A laser emitting section 12, a right-angle prism 24 for changing the direction of the laser beam emitted from the laser emitting section 12, and a rectangular prism 24 that converges the laser beam whose direction has been changed by the right-angle prism 24 onto the surface of a sample 16 made of molten steel or the like. A laser irradiation system 10 includes a condensing lens 14 for the laser beam, and a condenser for the sample emitted light to convert the light emitted from the surface of the sample 16 into light that propagates coaxially and in the opposite direction to the laser beam. Optical lens 26. The sample emitted light is collected using a spectrometer (
A beam block 28° having a laser beam transmitting part formed in the center thereof and a spectrometer system 18 consisting of a spectrometer are included to guide the laser beam to a laser beam (not shown). Somewhere along the way, coaxial devices have been developed. The former method is effective for the sample 16 having a smooth surface, but requires strict control of the position where the sample 16 is placed.

Moreover, according to the latter, even if the position of the sample 16 changes slightly.

The light emitted from the sample 16 can be guided to the spectrometer 22. However, in any optical system, if the distance between the sample 16 and the spectrometer 22 changes, the light emitted from the sample 16 cannot be efficiently guided to the spectrometer 22, and the distance between the sample 16 and the spectrometer 22 changes. The disadvantage is that the distance between them cannot be set arbitrarily.

The present invention was made to solve the above-mentioned conventional drawbacks, and the distance between the sample surface and the spectrometer can be set arbitrarily, and therefore, various restrictions on the installation of the spectrometer in a factory etc. can be set. It can be applied anywhere. The purpose is to provide a highly versatile laser emission spectrometer.

The present invention provides a laser emission spectrometer that uses a spectrometer to spectrally analyze light emitted from a sample surface when a laser beam is irradiated from a laser emitting part, and a method for converging the laser beam on the sample surface. A condenser lens and a condenser lens disposed outside the condenser lens. A concave annular mirror and a convex annular mirror for converting the light emitted from the sample surface into an annular parallel beam propagating coaxially and in the opposite direction to the laser beam, and at least a spectrometer optical system are provided, and a condenser lens, The above objects are achieved by making the laser beam and sample emitted light between the annular concave mirror and the annular convex mirror and the spectrometer optical system coaxial and parallel to each other.

Hereinafter, two embodiments of the present invention will be explained in detail with reference to the drawings.

In this embodiment, as shown in FIG.
The light emitted from the surface of 6 is transmitted to spectrometer 2 of spectrometer system 18.
2, a right-angle prism 24 for changing the irradiation direction of the laser beam 13 emitted from the laser emitting section 12 is used in an emission spectrometer using a laser for spectroscopic analysis.
Then, the laser beam 13 on the output side of the right angle prism 24 is directed to the sample 16.
a condenser lens 32 for converging the light onto the surface of the sample 16; and an annular parallel light beam disposed outside the condenser lens 32 that propagates the light emitted from the surface of the sample 16 coaxially with the laser beam 13 in the opposite direction. 37, an annular concave mirror 34 and an annular convex mirror 36, and 1 disposed outside the laser 13.
Sample emission light 37 converted into circular consonant rays? :Spectrometer 22
an annular concave mirror 4 for imaging into an entrance slit 42 of the
a spectrometer optical system 20 consisting of a spectrometer 20, a spectrometer 22, a photodetector 44 for detecting the intensity of the spectral lines separated by the spectrometer 22 disposed behind the spectrometer 22; The optical lens 321 is provided with a lens barrel 46 in which a mating portion 46a is formed in the intermediate portion to make the distance between the annular concave mirror 34 and the annular convex mirror 36 and the spectrometer optical system 20 variable. .

The laser emitting unit 12 emits a pulsed laser beam having a predetermined output and pulse width, for example.

Ruby laser with wavelength 0.69 μm, wavelength 1.05 to 1
．． A 0.6 μm infrared laser is used. A mode locking mechanism is incorporated into this laser emitting unit 12, and the mode of the laser beam 13 is adjusted to a Gaussian distribution type T E M o o
It is desirable to fix the mode.

The right angle prism 24 is for aligning the optical axes 'Th of the laser irradiation system 10 and the spectrometer system 18.

If the laser emitting section 12 is installed in a direction perpendicular to the surface of the sample 16, this step can be omitted.

The condensing lens 32 converges the laser beam 13 onto the surface of the sample 16 at its focal point.

The annular convex mirror 36 is coaxially arranged inside the inner diameter of the one annular concave mirror 34 and outside the condenser lens 32 . The curvatures of the annular concave surface @ 34 and the annular convex mirror 36 are such that the light emitted from the sample 16 is the same.

The combination is such that it can be transmitted coaxially with the laser beam 13 and in parallel in the opposite direction.

The annular concave mirror 40 of the spectrometer optical system 20 is.

It is arranged near the central axis of the laser beam 13 and is installed so as not to be irradiated with the laser beam 13 from behind.

This annular concave mirror 40 has a curvature that images the light 37 emitted from the sample 16 and made into parallel rays by the annular concave mirror 34 and the annular convex mirror 36 onto the entrance slit 42 of the spectrometer 22.

In the embodiment shown in FIG. 3, a five-ring concave mirror 40 is used.
For example, as in the first modified example shown in FIG. 4, one annular concave mirror 40 and a plane mirror 48 are combined, and only one annular concave mirror 40 is installed near the optical axis of the laser beam 13. And so on.

Depending on the wavelength of the spectrum to be measured, a beam splitter 50 and a convex lens 52 may be used, as in the second modification shown in FIG.
It is also possible to combine them.

The condensing system consisting of the condensing lens 32, one annular concave mirror 34, and one annular convex mirror 36 does not necessarily have to have the same focal length, and depending on the purpose, a lens or mirror of an appropriate value may be used. combination? Just use it. In particular, if the plasma emitted by laser irradiation expands above the sample surface, these two optical systems should be set at different focal lengths.

Light from plasma can be made into parallel light beams more accurately.

As the photodetector 44, for example, a photomultiplier tube, a photodiode, a photographic film, etc. are used.

In preparation for detecting a spectrum in the vacuum ultraviolet region, the lens barrel 46 has an argon atmosphere between the sample 16 and the condenser lens 32, and has an annular concave surface @34. A vacuum seal is applied between the annular convex mirror 36 and a vacuum is created between the condenser lens 32 and the spectrometer 22, or between the sample 16 and the spectrometer 22.
Optical force for sealing the argon gas introduction part 46b and the laser light introduction part so that the entire space is surrounded by argon.
The rear stage of the entrance loss slit 42 of the white glass 4 and the spectroscope 22 is sealed. Vacuum sealing glass 56 made of CaF, etc.
is provided.

The action will be explained below.

First, the lens barrel 4 including the condenser lens 325 and the spectrometer optical system 20
6 is adjusted so that the sample 16 is at the focal point of the condensing lens 32. At this time,
At the same time, the sample 16 automatically reaches the focal point of a condensing system consisting of an annular concave mirror 34 and an annular convex mirror 36. next,
The laser emitting unit 12 is activated to emit laser light 13 with a predetermined intensity and pulse width. Then, the laser beam 13 becomes
The light is guided through a right-angle prism 24 to a condensing lens 32 and focused on the surface of the sample 16. As a result, the laser irradiated area of the sample 16 instantly turns into plasma and emits light. This sample emitted light is transmitted to the annular concave mirror 34 and the annular convex mirror 3.
The combination of 6 produces an annular parallel beam 37, which is guided to the entrance slit 42 of the spectrometer 22 by the annular concave mirror 40 of the 5 spectrometer optical system 20. Inside the spectrometer 22, light is dispersed by a diffraction grating, prism, etc., and the spectral line intensity of the element to be measured is read by a photodetector 44, data processed by a conventional method, and converted into an analytical value.

According to this embodiment, the laser beam 13 with a wavelength of 1.06 μm, 1 output, 2 J%, and a pulse width of 15 nsec, emitted from the laser emitting unit 12, is converged by the condenser lens 32 with an aperture of 30 mm and a focal length of 150 mm, and the laser beam 13 is emitted from the sample 16. The emitted light is collected by an annular concave mirror 34 with an outer circle radius of 50 m and an inner circle radius of 35 am.
As a parallel ray 37 with a 5+m annular convex mirror 36,
The light emitted from sample 16 from the Fee binary alloy,
Fe spectral line intensity of 271.4 nm and 193
．． When the Onm C spectral line intensity was measured by changing the distance between the sample 16 and the spectrometer optical system 20, the force results shown in FIG. 6 were obtained. The space between the sample 16 and the vacuum seal glass 56 is filled with argon.

As is clear from Figure 6, considering that the laser output fluctuates by about 10%, the intensity of all spectral lines is approximately constant, regardless of the distance between the spectrometer and the material. I understand.

As explained above, according to the present invention, highly accurate measurements can be performed regardless of the distance between the sample and the spectrometer. Therefore, it can be applied to places where there are various restrictions on the installation of a spectrometer, such as in a factory, and has the excellent effect of increasing versatility.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the arrangement of the laser irradiation system and spectrometer system in an example of a conventional laser emission spectrometer, and Fig. 2 shows the arrangement of the laser irradiation system and spectrometer system in another example. 3 is a sectional view showing the configuration of an embodiment of the laser emission spectrometer according to Kinoi (11), and FIG. 4 is a front view showing the arrangement of the spectrometer optical system in the first modification. FIG. 5 is a front view showing the arrangement of the spectrometer optical system in the second modified example, and FIG. 6 is a front view showing the arrangement of the spectrometer optical system in the second modification. FIG. 2 is a diagram showing an example of the relationship between the spectral line intensities of Fe and C and the distance between spectrometer optical systems. 10... Laser irradiation system, 12... Laser emission section. 13... Laser light, 16... Sample, 18... Spectrometer system. 20... Spectrometer optical system, 22... Spectrometer, 32...
- Condensing lens, 34... Annular concave mirror, 36... Annular convex mirror, 37... Sample emission light, 40... Annular concave mirror, 42... Entrance' slit, 44... Light Detector, 46... Lens barrel, 46a... Grinding part, 48...
...Plane mirror, 50...Beam splitter, 52...
convex lens. (12) Figure 4 Figure 6 □ Distant Mankai (m)

Claims (1)

[Claims] (1) In a laser emission spectrometer that spectrally analyzes the light emitted from the sample surface when a laser beam is irradiated from the laser emitting part using a single spectroscope, there is a method for focusing the laser beam on the sample surface. A condenser lens and a condenser lens disposed outside the condenser lens. a circular concave mirror and a circular convex mirror for converting the light emitted from the sample surface into circular parallel light rays propagating coaxially and in the opposite direction to the laser beam; A spectrometer optical system is provided for guiding sample emitted light converted into an annular parallel beam to a spectroscope, and the laser beam and sample emitted light between the condenser lens, annular concave mirror, and annular convex mirror and the spectrometer optical system are
A laser emission spectrometer characterized by being coaxial and parallel to each other.