JPS649564B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a spectrometer for performing trace analysis of gases or liquids, which improves the sensitivity, accuracy, and stability of conventional spectrometers, and at the same time reduces the manufacturing cost. This relates to a spectrometer that significantly reduces the In particular, it is very effective to apply automatic measuring instruments for measuring the three components of sulfur dioxide gas (SO ₂ ), nitrogen monoxide (NO), and nitrogen dioxide (NO ₂ ), which are pollutant gases in flue gas.

Spectrometers that are technically similar to the spectrometer of the present invention are those disclosed in Japanese Patent Publication No. 62-11295 (Patent No. 1404332) and Japanese Patent Application Laid-Open No. 52-117178.

The spectrometer disclosed in Japanese Patent Publication No. 62-11295 only describes the measurement of one component gas, and does not describe any unique technique for simultaneously measuring multiple components.

Furthermore, the spectrometer disclosed in JP-A No. 52-117178 uses a cell with a built-in repeating reflection optical device, which is effective for measuring low concentration gas substances in the ambient atmosphere. The concentration of pollutants in the flue is much higher than in the ambient air, so even if the absorption optical path length is short, the sensitivity is sufficient and a single optical path cell is sufficient. Automatic measurement of the three components of pollutant gas (SO ₂ , NO, NO ₂ ) in the flue was performed using a spectrometer in which the cell of this spectrometer was replaced with a single optical path cell, and the results were very good.

In other words, it was demonstrated that the sensitivity, accuracy, and stability are good, and that the frequency of various types of maintenance including zero calibration and span calibration is significantly reduced compared to conventional automatic concentration measuring instruments. This technology simultaneously measures the second-order differential values of fine structure spectra at multiple wavelengths, and provides an analyzer that can simultaneously measure multiple components of gaseous substances with high sensitivity and has little interference from other components. be.

[Problem to be solved by the invention]

However, in the spectrometer disclosed in JP-A No. 52-117178, the wavelength modulator was of the exit slit vibration type, and two wavelength modulators were used to vibrate the three exit slits simultaneously, so the price of the wavelength modulator was low. is high. Furthermore, since it is necessary to pre-cut two or more exit slits on one slit plate, the wavelength spread of the spectrometer must match the pitch of the slits. For this reason, spectrometers are required to be manufactured with high precision, which increases the price. Furthermore, the spherical mirror, diffraction grating, etc. in the spectrometer are required to have high dimensional accuracy, which increases the price. Even if manufactured in this way, the exit slit still needs to be slightly moved in the lateral direction to adjust the wavelength, which necessitates a fine movement mechanism for finely moving the entire wavelength modulator, which is expensive. Furthermore, since the exit slit is vibrated, it is necessary to use a head window type photomultiplier tube as a photoelectric converter, and a low-cost side-on type photomultiplier tube cannot be used.

As described above, although it has been proven that the product has good performance and reduces maintenance costs, it has not been put into practical use due to the high product price.

The problem with the prior art is that the optical axis adjustment cannot be made as simple as it is for multi-component measurements.The present invention solves this drawback of the prior art and provides a spectroscopy system that is significantly lower in price. The purpose is to provide equipment.

[Means to solve the problem]

In order to achieve the above object, in particular, in order to facilitate optical axis adjustment, the spectroscopic device of the present invention has a wavelength modulator disposed within the spectroscopic device, and the exit slit is fixed or fixed after adjustment. This makes it possible to use a type photomultiplier tube, and the exit slits corresponding to the object to be measured and each component contained in the pollutant gas in the flue gas are carved on separate slit plates, and the positions of the individual exit slits can be finely adjusted. A group of exit slits that can be adjusted are constructed. In addition, a dedicated exit slit was installed for optical axis adjustment. That is, by providing an exit slit for optical axis adjustment in the exit slit plate for optical axis adjustment in the spectrometer, and by providing an optical axis adjustment marker if necessary, the optical axis adjustment of the spectrometer can be facilitated. At the same time, the fine adjustment mechanism of the spectrometer was reduced to only the fine adjustment mechanism of the exit slit.

[Effect]

In particular, how the problem of optical axis adjustment is solved by the present invention will be explained.

FIG. 1 is a diagram for explaining a conventional optical axis adjustment method of a spectrometer, and the conventional optical axis adjustment method of a spectrometer will be explained along this diagram.

Generally, the optical axis adjustment of the spectrometer 10 is performed by inputting incoherent visible light 2 from a light source 1 through an entrance slit 11 to a collimator mirror 12, and uniformly irradiating the entire collimator mirror with the incident visible light 2. The light source 1 is arranged as follows. Further, the collimator mirror 12 is finely adjusted so that the reflected light beam uniformly illuminates the diffraction grating 13. This fine adjustment is generally performed by three-point adjustment. Next, the direction of the grating plane of the diffraction grating is adjusted by rotating it in the α or β direction so that the entire collector mirror 14 is uniformly irradiated with the zero-order diffracted light from the diffraction grating 13. General scanning spectrometers have this fine adjustment mechanism, so this can be done easily. Next, the collector mirror 14 is finely adjusted so that the reflected light beam from the collector mirror 14 forms an image on the exit slit 15, and the process ends. However, in a non-scanning spectrometer, since there is no fine adjustment mechanism for the diffraction grating, the optical axis adjustment after the diffraction grating cannot be performed using conventional methods.

FIG. 2 is a diagram showing a method for adjusting the optical axis of an embodiment of the spectroscopic device according to the present invention, and the method for adjusting the optical axis will be explained along the figure.

Radiant light from a light source 3 that emits bright lines is made to enter the spectrometer 20 through an entrance slit 21. 29
is a refraction plate torsional vibration type wavelength modulator, but this wavelength modulator 29 is removed. The light source 3 is arranged so that the incident light beam from the light source 3 uniformly illuminates the entire mirror surface of the collimator mirror 22, and the collimator mirror is arranged so that the reflected light beam from the collimator mirror 22 uniformly illuminates the entire grating surface of the diffraction grating 23. Adjust 22.

This adjustment can be made by maintaining manufacturing accuracy to some extent, making the hole slightly larger, and moving the mount of the collimator mirror 22 within the hole.

Next, in order to adjust the diffraction grating 23, an optical axis adjustment marker 57 (hereinafter referred to as "marker") is placed in advance at the position where the zero-order diffracted light 4 is irradiated, and the entire marker 57 is uniformly spaced. The diffraction grating 23 is adjusted so as to irradiate the light. This adjustment of the diffraction grating 23 can also be carried out by moving it in the hole in the same way as the adjustment of the collimator mirror 22.

Furthermore, an exit slit 2 for adjusting the optical axis is fixed at a position where the bright line 8 emitted from the light source 3 should exit.
6, the collector mirror 2 is arranged so that the bright line is emitted.
Perform the optical axis adjustment in step 5. This adjustment is also done using the collimator mirror 2.
This can be done in the same way as adjustment 2. After the adjustment is completed, the wavelength modulator 29 is installed.

The above adjustment can be easily performed by adjusting the optical axis within the spectrometer. Furthermore, there is an exit slit 2 for measuring each component.
7, 27', 27'' remains to be adjusted, but these adjustment of the measuring exit slits is done after the entire spectrometer is assembled.

[First Embodiment] FIG. 3 shows an embodiment of the present invention, which will be explained along with this figure. A luminous flux emitted from a light source 5 passes through an absorption cell 6 and enters an entrance slit 21 of a spectrometer 20. The optical axis adjustment of this spectrometer 20 is performed as described above. The light beams emitted from the measurement exit slits 27, 27', 27'' of the spectrometer 20 are received by photoelectric converters 40, 40', 40'', respectively, and converted into electrical signals.

This electrical signal is received by the electrical signal processing device 100, and a DC voltage proportional to the degree of modulation of the light intensity modulation signal is output and displayed.

While observing this output DC voltage, the component gas to be measured is introduced into the absorption cell 6, and the measuring outlet slit 27 is adjusted so that the output DC voltage is maximized.
Move it slightly in the y-axis direction and fix it.

Next, another component gas to be measured flows into the absorption cell 6, and the measurement outlet slit 27' is adjusted. Furthermore, the measurement exit slit 27'' is adjusted in the same manner.

In FIG. 3, there is a wavelength modulator 29 between the entrance slit 21 and the collimator mirror 22, but it goes without saying that the same effect can be achieved even if the wavelength modulator 29 is located on the exit slit side.

[Second Embodiment] FIG. 4 shows another embodiment of the present invention, in which the wavelength modulator 29' is
This is a reflective mirror vibration type wavelength modulator that uses a letter-shaped tuning fork. To describe a specific example of this U-shaped tuning fork 30, the diameter is 1 to 2 mm, and the length of each leg is 15 to 2 mm.
30 mm, the distance between the legs is 4 to 10 mm, and the material of the legs is preferably piano wire.

A flat glass with a thickness of 1 mm or less and an area of 20 to 50 ^mm2 is glued to the free end of each leg so that the back of the glass is perpendicular to the center line of the foot. It is made into a mirror by attaching a metal vapor-deposited film. When bonding the flat glass to the free end of each leg, it is important to bond it symmetrically with respect to the midline between the two legs so as not to lower the Q of the tuning fork.

In this case, the optical axis adjustment is carried out after installing the wavelength modulator 29', and then using a reflector (mirror) 3 attached to the free end of one leg of the U-shaped tuning fork 30 of the wavelength modulator 29'.
1 is irradiated with light entering from the entrance slit 21,
Adjustments are made so that the reflected light beam from the reflecting mirror 31 uniformly illuminates the entire collimator mirror 22. This adjustment can also be made by moving inside the bakahole.

After this, the collimator mirror 22, the diffraction grating 23, the collector mirror 25, the measurement exit slits 27, 27',
27'' etc. may be adjusted using the method described above.

Conventionally, there have been examples of using a galvanometer-type vibrating mirror on the optical path between the entrance slit and the collimator mirror, but since galvanometers cannot maintain a high Q of vibration, the drive circuit (oscillator) has a highly stable frequency. However, since galvanometers use bearings, they can be damaged if operated continuously at high frequencies for long periods of time.

There is also a tuning fork that attaches a transparent glass plate to the free end of one leg and uses the refraction of the light as it passes through the glass plate to vibrate the output beam, but this type has a wavelength modulation of about 20 Å. The vibration amplitude of the tuning fork is over 100 mrad to obtain the width, which is unreasonable for practical use.

Further, if the transparent plate was attached only to the free end of one leg, there were drawbacks such as the balice of the tuning fork being damaged and Q being deteriorated.

On the other hand, when using the wavelength modulation type of the present invention in which a mirror is attached to the free end of the leg of a U-shaped tuning fork, (1) a vibration amplitude of about 2 mrad is sufficient, making it possible to construct a vibrating mirror with a frequency as high as 3 KHz; can.

(2) Also, since this level of amplitude is within the fatigue limit, the life is semi-permanent.

(3) It is possible to configure a vibrating mirror with a Q value of over 200, and during synchronous detection, it is possible to perform synchronous detection after passing through a high Q bandpass filter, increasing noise removal efficiency. This allows measurement with a good S/N ratio.

(4) Since the tuning fork does not have a rotating mechanism, the optical axis does not shift once it is fixed, making it possible to construct a spectrometer that is extremely stable over the long term.

(5) Also, no problem will occur even if it is operated continuously.

It is possible to construct a spectrometer with excellent features such as:

Further, the optical axis adjustment may be performed as shown in FIG. 5. In FIG. 5, the position of the laser light source is adjusted so that the light beam emitted from the laser light source 10 enters through the entrance slit 21 and irradiates the marker 51. In FIG. Next, this laser beam is transferred to the reflecting mirror 3.
The wavelength modulator 29' is attached, adjusted, and fixed so that the reflected light beam illuminates the center of the marker 1 and further illuminates the next marker 52 with this reflected light beam. After completing the adjustment, the markers 51 and 52 on the optical path are removed, and then adjustment is made so that the reflected light beam from the collimator mirror 22 illuminates the marker 53.

The marker 53 is removed, and then the diffraction grating 23 is adjusted so that the zero-order diffracted light from the diffraction grating 23 illuminates the marker 54.

Further, in order to adjust the collector mirror 25, the position of the laser light source 10' is adjusted so that the emitted light beam from the laser light source 10' enters through the measurement exit slit 27' and illuminates the marker 55. Next, this marker 55 is removed, the collector mirror 25 is adjusted so that the reflected light beam from the collector mirror 25 illuminates the marker 56, and the marker 56 is removed. This completes the optical axis adjustment within the spectrometer. The exit slit may be adjusted in the same manner as described above.

The optical design of the spectroscopic device described above is all done by simulation, and the position coordinates and optical paths of each optical component are accurately calculated. Therefore, it is only necessary that the position coordinates of the marker are calculated in advance, and the marker can be attached to that coordinate position. Furthermore, in order to reduce the manufacturing cost of the spectroscopic device, the dimensions of each optical component, the positions of mounting holes, etc. are determined based on general tolerances, so the placement position of each component inevitably deviates from the designed value. The above-mentioned adjustment method is to compensate for this deviation by using a slightly larger blind hole range. Furthermore, even with such adjustment, there is a slight deviation from the simulation result, so the wavelength spread at the dispersion spectrum imaging position (on the exit slit plate) will not be as calculated. Therefore, all but one exit slit are finely adjusted to apply to the wavelength spread of the completed spectroscopic device.

[Characteristic configuration in the example]

FIG. 6 shows an example of the optical axis adjustment marker 50. 1
5 is a laser beam, and 58 is a pin, which is inserted into a hole made in the bottom plate of the spectrometer.

〔effect〕

As described above, according to the present invention, the exit slit is divided into a group of exit slits for measurement and a slit dedicated to optical axis adjustment, and the position of the wavelength modulator is specified.

Furthermore, the exit slit group for measurement consists of at least one slit arranged at the emission position of the spectrum corresponding to each measuring substance (it is better to have two or more slits with different shapes or the same shape depending on the measuring substance). It consists of exit slits (slits), each of which can be adjusted in position laterally. In addition, by adopting a marker for optical axis adjustment, it was possible to put into practical use the optical axis adjustment of a spectrometer for multi-component measurement.

To describe the effects in detail: (1) Since the wavelength modulator is placed between the entrance slit and the collimator mirror, only one wavelength modulator is required (achieving no interference due to the unity of the driving part) .

(2) Since the exit slits were fixed, each slit plate had slits for one component so that the position of each slit plate could be finely adjusted. For this reason, a fairly large error with respect to the design values of the optical arrangement and optical axis of the spectrometer is allowed, and manufacturing accuracy may be within general tolerances. Similarly, general tolerances are allowed for the dimensional accuracy of optical components.

(3) Since the exit slit is fixed, it becomes an inexpensive side-on type spectrometer.

(4) The optical axis of the spectrometer can be easily adjusted by using a marker. For this reason, it has become possible to create a spectroscopic device for multi-component measurement that is equipped with multiple exit slits and has low manufacturing precision.

(5) An exit slit 26 for adjusting the optical axis is provided at the position where the emission line 8 of a known wavelength is to be emitted, and this is used to adjust the direction of the collector mirror 25, so the wavelength spread can be adjusted in the optical design. Optical axis adjustment of the spectrometer can be completed in almost the same state. Therefore, later adjustments can now be made by fine lateral adjustment of the measurement exit slits 27, 27', 27''.As a result, multi-wavelength differential values at multiple wavelengths that require high wavelength adjustment accuracy can be adjusted. Measurement is now possible.

The above effects can be obtained and an inexpensive automatic pollution meter can be provided.

The spectrometer of the present invention can be used to detect pollutant gases (SO ₂ ,
When applied as an automatic three-component measuring instrument (NO, NO ₂ ), accurate measurement is possible because the measurement principle is a purely physical method. Also, maintenance frequency can be reduced. Furthermore, since the spectrometer of the present invention is highly stable, the frequency of zero and span calibrations can be greatly reduced. Conventional automatic measuring instruments measure SO ₂ , NO,
Two automatic measuring instruments are required to measure NO ₂ .
Each required maintenance. however,
If the spectrometer of the present invention is used, the maintenance required for one conventional automatic measuring instrument can be further halved. Furthermore, it is possible to provide an automatic measuring device that is cheaper than the cost of two conventional automatic measuring devices.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional method for adjusting a spectrometer, and FIGS. 2, 3, 4, and 5 are diagrams showing an embodiment of a spectrometer for multicomponent measurement according to the present invention. FIG. 6 is a diagram showing an example of a marker used in an embodiment of the spectrometer for multi-component measurement according to the present invention. In the figure, 5 is a light source, 6 is an absorption cell, 21 is an entrance slit, 22 is a collimator mirror, 23 is a diffraction grating, 25 is a collector mirror, 29 and 29' are wavelength modulators, 30 is a reflecting mirror, and 26 is an optical axis. Adjustment exit slits, 27, 27', 27'' are measurement exit slits, 40, 40', 40'' are photoelectric converters, 50, 5
Reference numerals 1, 52, 53, 54, 55, 56, and 57 indicate optical axis adjustment markers, and 100 indicates an electrical signal processing device.

Claims (1)

[Scope of Claims] 1. A light beam emitted from a light source is guided to an absorption cell containing a plurality of types of substances to be measured, and the light beam is caused to generate absorption spectra of the plurality of types of substances to be measured. a slit, an exit slit,
The optical output signal outputted from the exit slit is guided to a spectrometer 20 equipped with a wavelength modulator 29 that modulates the wavelength of the light beam by swinging the optical axis relative to the exit slit, and converts the optical output signal output from the exit slit into an electrical signal. For multi-component measurement, comprising a photoelectric converter 40 for converting, and an electrical signal processing device 100 configured to receive an output signal of the photoelectric converter and obtain an output display corresponding to the degree of modulation of a light intensity modulation signal. In a spectrometer; the entrance slit 21 of the spectroscopic device is composed of a single fixed slit, the spectroscopic device has a collimator mirror 22, and the wavelength modulator 29 is an entrance composed of the fixed single slit. slit and the collimator mirror 22
and the exit slits are respectively arranged at positions that image different predetermined absorption spectra generated in the absorption cell corresponding to the plurality of types of substances to be measured, and each exit slit is arranged in a lateral direction. a group of measurement exit slits 27, 27', 27'' that can be finely adjusted;
and an optical axis adjustment exit slit 26 for adjusting the optical axis of the spectrometer, and the photoelectric converter includes a plurality of slits provided corresponding to each slit constituting the measurement exit slit group. A spectrometer for multi-component measurement characterized by comprising photoelectric converters 40, 40', 40''. 2. A light beam emitted from a light source is guided to an absorption cell containing a plurality of types of substances to be measured, and the light beam contains the plurality of substances. After generating the absorption spectra of different types of substances to be measured, the light beam is passed through an entrance slit, an exit slit,
The optical output signal outputted from the exit slit is guided to a spectrometer 20 equipped with a wavelength modulator 29 that modulates the wavelength of the light beam by swinging the optical axis relative to the exit slit, and converts the optical output signal output from the exit slit into an electrical signal. For multi-component measurement, comprising a photoelectric converter 40 for converting, and an electrical signal processing device 100 configured to receive an output signal of the photoelectric converter and obtain an output display corresponding to the degree of modulation of a light intensity modulation signal. In a spectrometer; the entrance slit 21 of the spectroscopic device is composed of a single fixed slit, the spectroscopic device has a collimator mirror 22, and the wavelength modulator 29 is an entrance composed of the fixed single slit. slit and the collimator mirror 22
and the exit slits are respectively arranged at positions that image different predetermined absorption spectra generated in the absorption cell corresponding to the plurality of types of substances to be measured, and each exit slit is arranged in a lateral direction. a group of measurement exit slits 27, 27', 27'' that can be finely adjusted;
an optical axis adjustment exit slit 26 for adjusting the optical axis of the spectroscopic device; the spectroscope includes an optical axis adjustment marker 57 that is fixedly or removably provided; and the photoelectric converter A spectrometer for multi-component measurement characterized by comprising a plurality of photoelectric converters 40, 40', 40'' provided corresponding to each slit constituting a group of measurement exit slits.