JPH04315928A - Emission spectrophotometer - Google Patents

Abstract

PURPOSE:To provide an emission spectrophotometer capable of carrying out simultaneous multi-element analysis, optimum adjustment in sensitivity to peaks of spectral beams in a simple configuration, and efficient measurement and storage of light reception signals based on several spectral beams even if they are input intermittently. CONSTITUTION:A plurality of slide blocks 24 by which each end of optical fibers 22 is fixed are mounted so as to slide freely on a slide means 29 arranged along a line of respective spectral beam collecting positions 26, and at the other end of each optical fiber 22 a photo-electric converter 30 is arranged in correspondence with the slide blocks 24, whereby a light reception part 20 is constituted. A measuring part is provided to take only peak profile of light emission spectrum over a threshold value in a buffer memory by means of a judgement circuit.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical emission spectrometer.

0002

[Prior Art] Generally, in an emission spectrometer, a light emitting section excites a sample to emit light, a spectroscopic section separates this light into spectral light of each wavelength component, and the spectroscopic light unique to each element is transmitted to a light receiving section. Qualitative and quantitative analysis of the component elements of the sample is performed by receiving light, converting it into a corresponding electrical light reception signal, and extracting it, and processing these light reception signals in the measurement section.

In particular, when analyzing fine particles such as dust and gas components in the atmosphere using the above-mentioned emission spectrometer, gas containing fine particles such as dust and gas components in the chamber is sampled with a capillary tube. Then, this gas is mixed with a carrier gas and transferred to a reaction tube, and in this reaction tube, these gases are discharged and turned into plasma by microwaves supplied from a microwave power source, which causes them to be excited and emit light. Wave inductively coupled plasma (MI
Emission spectroscopic analysis using P) as an excitation light source may be performed.

[0004] In this type of analysis targeting fine particles such as dust and gas components, the sample is not supplied to the reaction tube without interruption like a liquid sample, but intermittently. become. Therefore, the peak of the emission spectrum obtained by exciting these fine particles to emit light occurs in a pulsed manner with a short time width of, for example, about 1 mm seconds when viewed on the time axis. Then, by measuring the emission spectrum of the fine particles mentioned above, we can identify their component elements, and by counting the number of peaks per predetermined time for each spectrum of light, we can analyze the concentration, composition, particle size, number, etc. of the sample. I try to do that.

By the way, the structure of the above-mentioned spectroscopic section is as follows.
Conventionally, there are so-called monochromators, which extract and receive only one of each spectrum of light separated by a diffraction grating, and so-called polychromators, which simultaneously receive each spectrum of light separated by a diffraction grating.

[0006]

[Problems to be Solved by the Invention] The former monochromator has the advantage of having a high degree of freedom in wavelength selection because it can temporally scan wavelengths and perform spectroscopic analysis by selecting any wavelength. The disadvantage is that it is not possible to simultaneously receive and analyze spectral light of multiple wavelengths within a given time. In particular, in the analysis of fine particles as described above, since the emission spectrum is generated in a pulsed manner, it is difficult to scan the diffraction grating over a wide wavelength range in such a short period of time.

On the other hand, the latter polychromator is
Since a photoelectric converter such as a photomultiplier tube is installed in advance at the condensing position of each spectrum of light, there is an advantage that simultaneous multi-element analysis is possible. However, when it is necessary to measure spectral lights that are close to each other and have a wavelength difference of several nanometers, even if you try to place a photoelectric converter at the focal point of each spectral light, the photoelectric converter such as a photomultiplier tube will not work. , have a certain size, so they physically collide with each other, and therefore there is a limit to increasing the wavelength resolution.

[0008] To deal with this problem, it is possible to increase the distance between the diffraction grating and the photoelectric converter so that there is a sufficient distance difference between the light receiving positions, but with such a configuration, There is a problem that the entire spectroscopic section becomes large.

[0009] Therefore, a photo array sensor composed of a CCD or the like is used as a photoelectric converter, and this photo array sensor is two-dimensionally moved along the trajectory of the condensing position of each spectrum light separated into wavelengths by a spectrometer. A device has also been proposed in which a wide wavelength range can be measured continuously and simultaneously.

However, with this photo array sensor, it is not possible to individually adjust the sensitivity for each element's spectral light, making it difficult to perform high-sensitivity measurements focusing only on a specific element. In particular, when analyzing a gas containing fine particles as mentioned above, the sampling gas and carrier gas contain more particles than the fine particles, so if sensitivity adjustment is not possible, it is necessary to Measurement sensitivity is determined by the emission spectrum of the carrier gas and the like rather than the emission spectrum of the carrier gas, making it difficult to perform high-sensitivity measurements.

On the other hand, the measuring section that processes the received light signal conventionally receives and stores all the received light signals, including the background, based on each spectrum of light output from the light receiving section.

[0012] Therefore, especially when there are many spectral lights to be measured and it is necessary to shorten the sampling period of the light reception signal in order to count the number of peaks of each spectral light, such as in the analysis of fine particles. , a memory with a correspondingly large storage capacity is required, which increases the cost of the device.

[0013]

[Means for Solving the Problems] The present invention has been made in order to solve the above-mentioned problems, and it is possible to perform simultaneous multi-element analysis with regard to the spectroscopic section and the light receiving section, and it is further improved than before. In addition to having a compact structure, it is possible to perform optimal sensitivity adjustment to the peak of each spectrum light, and the measurement section is designed to be able to handle even when light reception signals based on multiple spectrum lights are intermittently input. , it is possible to efficiently measure and store these light reception signals.

Therefore, the present invention includes a spectroscopic section that separates the light emitted by the light emitting section into spectral light of each wavelength, and a spectroscopic section that receives each wavelength-separated spectral light in this spectroscopic section and generates a corresponding electrical signal. An emission spectrometer has the following configuration, and includes a light receiving section that converts the signal into a received light signal and outputs it, and a measuring section that processes the received light signal from the light receiving section.

That is, in the first invention, the light receiving section has a large number of slide blocks formed by fixing one end of an optical fiber, and each of these slide blocks moves along the trajectory of the condensing position of each spectrum light. The photoelectric converter is slidably attached to a slide mechanism provided in the slide block, and a photoelectric converter is arranged at the other end of each of the optical fibers in correspondence with the slide block.

Further, in the second invention, the measuring section compares each light reception signal from the light receiving section with each threshold value individually set according to those signals, and at least one of the light reception signals is detected. a determination circuit that outputs an input permission signal only during the period when the received light signal exceeds the threshold value when the corresponding threshold value is exceeded; The structure includes a buffer memory that also stores the received light signal.

[0017]

[Operation] According to the first invention, light is received by thin optical fibers, and the slide block to which each optical fiber is attached can be made thin to a thickness close to the outer diameter of the optical fiber. can be brought closer to each other. Therefore, the light receiving section can be made smaller, and the width of each wavelength of the received spectral light can be made smaller, making it possible to achieve high wavelength resolution. Furthermore, since a photoelectric converter is provided for each slide block to which each optical fiber is attached, sensitivity can be adjusted for each spectral peak, resulting in faster time response.

Further, according to the second invention, in the measurement section,
Only when the determination circuit obtains a peak profile of the emission spectrum that is equal to or higher than the threshold value, that data is taken into the buffer memory, so the memory that stores the received light signal requires less storage capacity, and the processing time is also shortened. An efficient and inexpensive device can be realized.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing the entire structure of a spectroscopic section and a light receiving section of an optical emission spectrometer according to an embodiment of the present invention.

In the figure, reference numeral 1 indicates the entire emission spectrometer, 2 is a light emitting section such as an ICP, 4 is a condenser lens, 6 is an entrance slit, and 8 is a light emitting section that converts the light from the light emitting section 2 into various wavelengths. This light receiving section 8 is of a closed Czerny-Turner type in this example, and includes a condensing mirror 10, a plane mirror 12, a plane diffraction grating 14, and a wavelength spectral imaging unit. It consists of a mirror 16.

Reference numeral 20 denotes a light-receiving section that receives each spectrum of light that has been wavelength-separated by the spectrometer 8, converts it into a corresponding electrical light-receiving signal, and outputs the signal. This light receiving section 20 has a large number of slide blocks 24 each having one end of a plurality of optical fibers 22 fixed thereto, and each of these slide blocks 24
is slidably attached to a slide mechanism 28 provided along the trajectory 26 of the condensing position of each spectrum light. The other end of each optical fiber 22 fixed to each slide block 24 is connected to a photoelectric converter such as a photomultiplier tube, which is connected to each slide block 24.
They are placed opposite each other on the front of the 0.

FIG. 2 is a perspective view showing a specific configuration of the light receiving section 20 at the condensing position of the spectral light.

In the figure, reference numeral 32 denotes a measuring tape that serves as a guide for determining the light receiving position of the optical fiber 22. Slide shafts 34 constituting the slide mechanism 28 are arranged on the left and right sides of this measuring tape 32, respectively, and a rack is attached to each slide shaft 34. 3
6 is formed. Note that the teeth of the rack 36 are formed to be slightly inclined with respect to the direction orthogonal to the axial direction of the slide shaft 34.

The measure 32 and the slide shaft 34 are arranged along the trajectory 26 (in the vertical direction in FIG. 2) of the condensing position of each spectrum light, and each slide shaft 3
4 is fitted with a slide block 24. One end of an optical fiber 22 is fixed to each slide block 24, and the end face of each of these optical fibers 22 is set to coincide with the condensing position of each required spectrum of light.

As shown in FIG. 3, the slide block 24 described above consists of a main body portion 38 that is fitted into the slide shaft 34, and a support portion 40 to which the optical fiber 22 is attached.

The support portion 40 is formed into a thin plate shape having an L-shape as a whole so as to be able to overlap each other in the axial direction of the slide shaft 34, and as shown in FIG. A large number of optical fibers 22 are arranged and fixed in an array between the plate 56 and the optical fibers 22 .

On the other hand, the main body portion 38 is formed with an insertion hole 42 for the slide shaft 34, a contact plate 44 is disposed in the insertion hole 42, and a guide groove 4 is formed continuously in the insertion hole 42.
8 is formed, and a position adjustment block 4 is formed in this guide groove 48.
6 is fitted. Furthermore, the position adjustment block 46
A tooth portion (not shown) that engages with the rack 36 is formed on the side facing the insertion hole 42 , and an adjustment screw 50 is connected to the position adjustment block 44 . As a result, when the adjustment screw 50 is turned, the position adjustment block 44 advances or retreats along the guide groove 48 as shown by the arrows, and the position adjustment block 44 engages and disengages from the rack 36 accordingly. Therefore, when the position adjustment block 44 is advanced, the teeth of the position adjustment block 44 bite into the rack 36, and the entire slide block 24 moves slightly upward in the figure along the slide shaft 34. However, this allows fine adjustment of the positioning of the slide block 24. Also,
The above-mentioned abutting plate 44 is connected to a fixing screw 52, and by screwing in this fixing screw 52, the abutting plate 44 is attached to the slide shaft 3.
4, so that the slide block 24 can be fixed to the slide shaft 34 after position adjustment.

In the optical emission spectrometer having the above configuration, the light from the light emitting section 2 is focused by the condenser lens 4, and is incident on the spectroscopic section 8 through the entrance slit 6. This incident light is
It becomes parallel light by the condensing mirror 10, and the plane mirror 12
The light is reflected by the beam and irradiated onto the plane diffraction grating 14. The plane diffraction grating 14 splits this light into spectral lights having different diffraction angles depending on each wavelength, so these spectral lights are focused by the wavelength spectroscopic imaging mirror 16 at a position corresponding to each wavelength. .

Since the end face of the optical fiber 22, which has been adjusted in advance by the slide block 24, is installed at the condensing position of each spectrum light corresponding to the element contained in the sample, each spectrum light is introduced into the optical fiber 22. and guided to the photoelectric converters 30, where each photoelectric converter 30 converts it into an electrical signal.

In the light receiving section 20, the slide block 2
The support portions 40 of No. 4 are made thin in advance to a thickness close to the outer diameter of the optical fiber 22, and when these support portions 40 are stacked on top of each other, the distance difference between the light receiving positions is extremely small, and the distance difference between the light receiving positions is extremely small. Since spectral lights with close wavelengths can be received individually, high wavelength resolution can be obtained. For example, if an optical fiber 22 with an outer diameter of 0.1 mm is used, the thickness of the support portion 40 can be approximately 1 mm, and the focal length from the diffraction grating 14 is set to 0.5 m. It is also possible to receive spectral lights with wavelength differences on the order of nanometers and below the decimal point, and high wavelength resolution can be achieved despite the small size. Moreover, since the photoelectric converter 30 is provided for each slide block 24 to which each optical fiber 22 is attached, sensitivity adjustment can be performed according to the intensity of each spectrum of light, and as a result, the time response becomes faster.

In this example, the slide shaft 36 is provided in a straight line; however, depending on the characteristics of the diffraction grating 14, the setting of the target spectral wavelength range, etc., a straight shaft may not be suitable. Sometimes it is also possible to have an arcuate shape.

FIG. 5 is a block diagram showing the configuration of a measuring section according to an embodiment of the present invention.

In the figure, reference numeral 58 indicates the entire measuring section, 60 an amplifier for amplifying the light reception signal obtained by receiving the spectrum light with each photoelectric converter 30 of the light receiving section 20;
2 is an A/D converter that digitizes each light reception signal. Further, 64 compares each digitized received light signal with each threshold individually set according to those signals, and if at least one received light signal exceeds the corresponding threshold, A determination circuit 66 outputs an input permission signal only during a period when the light reception signal exceeds a threshold value.
This is a buffer memory that stores each light reception signal together in response to an input permission signal from 4. 68 is a buffer memory 66
This is a signal processing unit that identifies the composition and size of the sample and quantifies its concentration, etc., based on the data captured in the sample.

In the above configuration, for example, when measuring fine particles such as dust or impurity gas as a sample, the light receiving section 2
Each spectrum light corresponding to each component element received at 0 is
When viewed on the time axis, it occurs in a pulse-like manner with a short time width of, for example, about 1 mmsec. A light reception signal output from the photoelectric converter 30 based on each of these spectrum lights is applied to a determination circuit 64 and a buffer memory 66 via an amplifier 60 and an A/D converter 62, respectively.

The determination circuit 64 compares each received light signal with a threshold value individually set according to each of the signals, and
When at least one of the light reception signals exceeds its corresponding threshold, the input permission signal s1 is output for only the period during which the light reception signal exceeds the threshold. In response to this input permission signal s1, the buffer memory 66
stores all the light reception signals from each A/D converter 62. Therefore, in the buffer memory 66, not only the light reception signal exceeding the threshold value but also other light reception signals are stored at the same time.

On the other hand, in a state where no emission spectrum based on fine particles is generated, all the light reception signals are below their respective thresholds, so in this state, the determination circuit 6
4 does not output the input permission signal s1, and therefore the light reception signal is not stored in the buffer memory 66. That is,
In a background state where an emission spectrum from the sample cannot be obtained, data is not loaded into the buffer memory 66, so the data memory capacity in the signal processing section 68 can be reduced.

Then, the signal processing section 68 takes in the received light signal data based on each spectrum light stored in the buffer memory 66 within a short time, identifies the composition of the sample from the peak wavelength of the spectrum light, and also identifies the peak height. Processes such as analyzing the size of the fine particles and further analyzing the concentration etc. by counting the number of spectral peaks per predetermined time are performed.

[0038]

[Effects of the Invention] The present invention has the following effects.

(1) According to the first invention, light is received by thin optical fibers, and the slide block to which each optical fiber is attached can be made thin to a thickness close to the outer diameter of the optical fiber. Blocks can be moved closer together. Therefore, the light receiving section can be made smaller, and the width of each wavelength of the received spectral light can be made smaller, making it possible to achieve high wavelength resolution. Furthermore, since a photoelectric converter is provided for each slide block to which each optical fiber is attached, sensitivity can be adjusted for each spectral peak, resulting in faster time response. Therefore, especially when analyzing the composition of fine particles, it is possible to avoid the inconvenience that measurement sensitivity is determined by the emission spectrum of carrier gas, etc., and high-sensitivity measurement becomes possible.

(2) According to the second aspect of the invention, in the measurement section, only when the determination circuit obtains a peak profile of the emission spectrum that is equal to or greater than the threshold, the data is taken into the buffer memory, so that the received light signal is not stored. The storage capacity of the memory used for this purpose is small, and the processing time is also shortened, making it possible to realize an efficient and inexpensive device. Therefore, it is particularly effective when counting the number of peaks per predetermined time in the emission spectrum of the fine particles to analyze the concentration of each component composition of the fine particles.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the entire spectroscopic section and light receiving section of an optical emission spectrometer according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a specific configuration of a light receiving section at a light condensing position according to an embodiment of the present invention.

FIG. 3 is a perspective view of a slide block of the light receiving section in FIG. 2;

FIG. 4 is an enlarged front view of section A of the slide block in FIG. 3;

FIG. 5 is a block diagram showing the configuration of a measuring section according to an embodiment of the present invention.

[Explanation of symbols]

1... Emission spectrometer, 2... Light emitting section, 8... Spectroscopic section, 20
. . . Light receiving section, 22 .

Claims (2)

[Claims] Claim 1: A spectroscopic section that separates the light emitted by the light emitting section into spectral light of each wavelength, and a spectroscopic section that receives each of the wavelength-separated spectral lights and generates a corresponding electrical light reception signal. In an optical emission spectrometer equipped with a light receiving section that converts and outputs the signal, and a measuring section that processes the received light signal from the light receiving section, the light receiving section has a number of slide blocks each having one end of an optical fiber fixed thereto. Each of these slide blocks is slidably attached to a slide mechanism provided along the trajectory of the focusing position of each of the spectral lights, and the other end of each of the optical fibers is individually attached to the slide block. An optical emission spectrometer characterized in that a photoelectric converter is arranged in accordance with the configuration. 2. A spectroscopic section that separates the light emitted by the light emitting section into spectral light of each wavelength, and a spectroscopic section that receives each wavelength-separated spectral light and converts it into a corresponding electrical light reception signal. In an optical emission spectrometer that includes a light receiving section that converts and outputs the signal, and a measuring section that processes each received light signal from the light receiving section, the measuring section converts each received light signal from the light receiving section according to the signals. When at least one received light signal exceeds the corresponding threshold value, the input permission signal is output only during the period when the received light signal exceeds the threshold value. What is claimed is: 1. An optical emission spectrometer comprising: a determination circuit that outputs a signal; and a buffer memory that stores each of the received light signals in response to the input permission signal from the determination circuit.