JPH11183387A - Emission spectroscopic analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high wavelength resolution over a wide wavelength range without deteriorating sensitivity. SOLUTION: In a portable or small emission spectroscopic analyzer, an image sensor 9 may be used as a detector for detecting the spectral light obtained by spectrally dispersing the luminescence of a sample S. The wavelength received by the image sensor 9 is switched in step by largely switching the rotation angle of a diffraction grating of displacing the image sensor 9 in step in the wavelength direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emission spectrometer and, more particularly, to an improvement in a part for spectrally analyzing the emission of a sample and detecting the spectrum light.

[0002]

2. Description of the Related Art Conventionally, an emission spectrometer that discharges and emits a metal sample and spectrally analyzes the emission is provided with a large-sized or immovable sample so that it can be analyzed at the site where it exists. Some are made smaller and portable.

In such a portable emission spectrometer, a portion which directly acts on a sample S and discharges and emits the sample S is provided separately from a device main body 21 as a probe 22, as shown in FIG. .

The probe 22 is usually of a pistol type.
A discharge light emitting space 23 is formed inside the distal end, and a needle-like discharge electrode 24 projects into this space.

At the time of analysis, the tip of the probe 22 may be pressed against the sample S, and there is no need to move the sample S. When a high voltage is applied to the discharge electrode 24 with the probe 22 pressed against the sample S, an arc discharge or a spark discharge occurs between the sample surface and the discharge electrode 24, and the sample S emits light by excitation. The light emitted from the sample S is taken into the spectral detection unit 25 provided in the apparatus main body 21 through the optical fiber 26 and is separated into spectrums, and the intensity of each spectrum light is measured.

Incidentally, in such a portable emission spectrometer, in order to reduce the size of the device, the spectrum detector 25 is required.
There is a detector using an image sensor such as a CCD or a photodiode array as a detector of the spectrum light in the above. Since the image sensor detects each of the long and short spectrum light at each pixel, which is a pixel unit, the spectral detection unit is much smaller than the conventional one using a detector such as a photomultiplier. In addition, the size of the entire apparatus can be reduced.

[0007]

However, the above-mentioned emission spectrometer using an image sensor has a problem that a high wavelength resolution cannot be obtained in a wide wavelength range.

Now, assuming that the number of pixels provided on one image sensor is N and the total wavelength range of light incident on all light receiving surfaces of this image sensor is Δλ, the wavelength range Δλ _P per pixel is , Δλ _P = Δλ / N (a) From this equation (a), it can be seen that the larger the number N of pixels per element and the narrower the total wavelength range Δλ of incident light, the narrower the wavelength range Δλ _P per pixel and the higher the wavelength resolution. .

[0009] Of these, the entire wavelength range Δλ of the incident light on the image sensor corresponds to the wavelength range that can be measured as it is, and if it is narrow, the wavelength range that can be measured at one time becomes narrow, which is inconvenient.

In order to increase the wavelength resolution without narrowing the measurable wavelength range, it is necessary to increase the number N of pixels per element.

However, in the image sensor, it is difficult to increase the size of the element and lengthen the light receiving surface due to restrictions on the manufacturing as a semiconductor element, and there is a limit in increasing the number of pixels of the same size. The number is about 2000.

Of course, forming smaller pixels on an image sensor of a fixed length does not necessarily mean that the number of pixels cannot be increased, but this will reduce the light receiving area per pixel and reduce the sensitivity. descend.

As described above, since the length of the light receiving surface of the image sensor and the size of the pixel are limited, it is difficult to increase both the wavelength resolution and the sensitivity. At present, the required sensitivity is obtained in the wavelength range.

The present invention has been made in view of the above situation, and has as its object to realize high wavelength resolution over a wide wavelength range without causing a decrease in sensitivity.

[0015]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an emission spectroscopic analyzer using an image sensor as a detector for spectral spectrum light, wherein the image sensor has a relative position with respect to incident spectrum light. The configuration is such that a stepwise displacement in the wavelength direction is possible.

[0016]

FIG. 1 is a block diagram of a portable optical emission spectrometer according to an embodiment of the present invention, FIG. 2 is a schematic perspective view of a diffraction grating portion of the apparatus, and FIG. FIG. 4 is a configuration diagram of the spectral detection unit according to the embodiment, and FIG. 4 is a waveform diagram for explaining the operation.

As shown in FIG. 1, the portable emission spectrometer of this embodiment comprises a device main body 1 and a probe 2 provided separately from the device main body 1 as a portion acting on a sample S.
Consists of

The probe 2 has a portion which comes into contact with the sample S and emits discharge light therefrom, and is formed into a predetermined shape such as a gun type. The probe 2 has a cylindrical tip and has a discharge light emitting space 3 therein. Are formed, and a needle-shaped discharge electrode 4 is exposed in the space 3.

On the other hand, the apparatus main body 1 includes at least a circuit for supplying a high voltage for discharge to the probe 2, a circuit for processing a signal obtained by the probe 2, and light emission of the sample in the discharge light emission space 3. Is provided through an optical fiber 26, the light is spectrally separated, and a spectral detection unit 5 for detecting the intensity of each spectrum light is provided.

As the optical system of the spectral detection unit 5, for example, a Fasty-Evert type optical system is employed, which includes an entrance slit 6, a concave mirror 7, and a diffraction grating 8, and is used as a detector for spectrally separated spectral light. , An image sensor 9 such as a CCD or a photodiode array is used.

In the spectral detector 5, the spectral light reflected by the concave mirror 7 and incident on the image sensor 9 is incident on a wider area than the length of the light receiving surface of the image sensor 9. On the other hand, the image sensor 9 may have the same length as that used in the conventional portable emission spectrometer and the number of pixels may be about 1,000 or 2,000. There is no need to increase the number of pixels.

The diffraction grating 8 of the spectral detection section 5 is provided with a motor 10 as a rotation driving means and an angle sensor 11.
As a result, the diffraction angle is switched in a stepwise manner, so that the light incident on the image sensor 9 is displaced stepwise along the wavelength direction, that is, the length direction of the image sensor 9. ing.

Specifically, as shown in FIG.
0 is directly connected to the rotation axis 12 of the diffraction grating 8,
2, a disk 13 having several slits 13s around its periphery is attached, and an angle sensor 11 such as a photo interrupter is provided at an outer peripheral position of the disk 13. And this angle sensor 11 is used for each slit 13s of the disc 13.
, The stepwise rotation of the diffraction grating 8 is controlled.

In the embodiment shown in FIG. 1, the light incident on the image sensor 9 is displaced stepwise in the wavelength direction by changing the rotation angle of the diffraction grating 8 significantly.
Either the image sensor 9 or the light incident thereon may be displaced in the wavelength direction. Therefore, as shown in FIG. 3, the image sensor 9 can be intermittently slid, that is, displaced stepwise in the wavelength direction with respect to the incident light.

In FIG. 3, reference numeral 14 denotes a linear motor mounted on the image sensor 9. The image sensor 9 is displaced stepwise in the wavelength direction of the incident light by driving the linear motor 14. In this embodiment, it is not necessary to switch the diffraction angle of the diffraction grating 8 in a stepwise manner, and it is sufficient that the angle can be simply adjusted. The other parts are the same as those of the spectral detector 5 of FIG.

In the above configuration, at the time of measurement, the tip of the probe 2 is pressed against the sample S, and a high voltage is applied to the discharge electrode 4 in that state. Then, discharge occurs between the discharge electrode 4 and the surface of the sample S, and the sample emits light by excitation. The emitted light is taken into the spectral detection unit 5 through the optical fiber 26, is separated by the diffraction grating 8, and the separated spectral light is received by the image sensor 9, and the intensity is detected.

In this case, the length of the light receiving surface of the image sensor 9 is shorter than the wavelength range to be detected, so that the image sensor 9 cannot detect the spectrum light in the required wavelength range at one time. Since the rotation angle of the grating 8 can be largely switched or the image sensor 9 can be displaced stepwise in the wavelength direction, the wavelength range of the spectrum light received by the image sensor 9 can be cut stepwise. Instead, this covers the entire wavelength range to be detected even with a single image sensor 9.

This will be described with reference to the waveform diagram of FIG.
For example, among the wavelength ranges to be detected, first, the spectral light in the wavelength range indicated by Δλ ₁ is received by the image sensor 9, and then the relative position between the image sensor 9 and the incident spectral light is significantly switched, The spectrum light of the wavelength range Δλ ₂ adjacent to the wavelength range Δλ _{1 is received so as} to partially overlap the Δλ ₁ , and finally, the spectrum light of the wavelength range Δλ ₃ is received by the same operation. Thus, the spectrum light in the wavelength range to be detected is received and detected.

Here, looking at the state of light reception at each stage,
A single image sensor 9 receives a part of a narrow wavelength range to be detected.

In the conventional apparatus, since the entire wavelength range to be detected by a single image sensor is received, the image sensor 9 according to the present invention receives spectral light in a narrow wavelength range. However, the wavelength range in which each pixel receives light is narrow, and the wavelength resolution is accordingly increased.

Several groups of detection signals are obtained by the above-described series of spectroscopy and detection. From these detection signals, data relating to the spectrum light in the entire wavelength range to be detected is generated by signal processing in the apparatus main body 1. Is done.

Regarding this processing, it is desirable that the overlapping portion of each of the detected wavelength ranges Δλ ₁ , Δλ ₂ , Δλ ₃ contains the spectral light of the internal target element. If there is a signal, the detection signal is corrected based on the signal, and the detection signals in each wavelength range can be integrated in a consistent manner.

It is needless to say that the present invention is not limited to a portable type, but may be applied to another type of emission spectrometer as long as an image sensor is used as a detector for spectral light. Further, in the above embodiment, the device body 21
The spectral detection unit 5 provided on the side may be provided in the probe 2.

[0034]

According to the present invention, the spectrum light in the wavelength range to be detected is divided into several ranges and received by a single image sensor, and the wavelength range that the image sensor receives at one time is narrow. Therefore, the wavelength range in which each pixel receives light is narrowed, the wavelength resolution is improved, and highly accurate analysis is possible.

Further, by switching the wavelength range of light received by the image sensor in a stepwise manner, a single image sensor can cover a wide wavelength range, and it is not necessary to form a small pixel of the image sensor. , Does not cause a decrease in sensitivity.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a portable emission spectrometer according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view of a diffraction grating portion of the device.

FIG. 3 is a configuration diagram of a spectral detection unit according to another embodiment of the present invention.

FIG. 4 is a waveform chart for explaining the operation of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional portable emission spectrometer.

[Explanation of symbols]

1 apparatus main body, 2 probes, S sample, 5 spectral detector, 8 diffraction grating, 9 image sensor, 10 motor, 11 angle sensor,

Claims (1)

[Claims] 1. An emission spectroscopic analyzer using an image sensor as a detector for spectral spectrum light, wherein the image sensor is provided so as to be capable of stepwise displacement in a wavelength direction relative to incident spectrum light. An emission spectrometer characterized by the above-mentioned.