JP3453260B2 - Laser wavelength setting device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a laser wavelength setting device required for a density and temperature measuring method using a laser induced fluorescence method (hereinafter also referred to as LIF). (LIF = Lasc
2. Description of the Related Art FIG. 7 shows a conventional apparatus. FIG. 7 is a diagram showing a conventional wavelength setting device, that is, a temperature and concentration analyzer using a general laser-induced fluorescence (LIF) method. In the laser induced fluorescence (LIF) method, it is necessary to irradiate the measurement field 120 with a laser beam having the same frequency as the absorption line of the measurement molecule. Oscillation is performed to output a laser beam having a wavelength corresponding to the electron energy difference between the measurement molecules. The laser beam is supplied to a beam expander 103.
After being formed into a sheet, the measurement field 120 is irradiated. The fluorescence generated by the excited measurement molecules is reflected on the lens 1
The light is condensed at 04 and measured by the CCD camera 105. The synchronization line 106 synchronizes the oscillation of the excitation pulse laser 101 with the CCD camera 105. CC
The signal from the D camera 105 is transferred to the computer 107, and the temperature and concentration are analyzed. In the conventional method for setting a wavelength corresponding to the electron energy difference of a measurement molecule, (A) a part of a laser beam is branched by a beam splitter 108 and (B) a lens 10
9, the laser light is condensed on the slit of the high-resolution spectroscope 110, and (C) the laser light is split and then measured by the line sensor 111, and (D) the computer 107
The absolute value of the wavelength was calculated by (E), and a wavelength corresponding to the electron energy difference of the measured molecule was set using the calculation result. However, the prior art has the following problems. (1) In the laser-induced fluorescence (LIF) method, it is necessary to match the wavelength of a laser beam with a precision of 0.001 nm to a wavelength corresponding to the electron energy difference of a measured molecule. Wavelength display device (accuracy:
0. (about 1 nm) cannot be set. (2) In order to determine the absolute value of the wavelength by the high-resolution spectroscope 110 as in the conventional method, the absolute value must be calibrated, and errors tend to occur due to a shift of the optical system. , There was a problem with accuracy. (3) In general, a high-resolution spectroscope has a large device (about 500 × 300 × 300 mm), so that it is difficult to make the device compact and the device is expensive. The present invention
An object is to provide a device capable of solving these problems. (First Means) A laser wavelength setting apparatus according to the present invention applies a laser beam to a measurement field 20, excites a molecule to be measured at an electron energy level, and excites the laser. An apparatus for measuring the concentration of two-dimensional and three-dimensional chemical species and measuring the temperature in the measurement field 20 by measuring light (fluorescence) generated from the emitted molecules, comprising: (A) a pulse laser 1 for excitation; Laser 2;
High temperature heating elements or discharging terminal encapsulated cell 3 while provided in the order, (B) the hot heating element or the discharge terminal encapsulated cell 3
Photodetector 5 and, (C) the hot heating element or the discharge terminal encapsulated cell 3 the light (fluorescence) input through the lens 4 from
Inputs light (fluorescence) from, a beam expander 7 which irradiates the measuring field 20 light (fluorescence), CCD camera 9 to enter through the lens 8 the light (fluorescence) from (D) the measuring field 20 When a signal from the optical detector 5 (E), the CCD camera 9
Receives a signal from, a computer 6 for outputting the excitation pulse laser 1, a, a synchronization line 10 synchronizes the CCD camera 9 (F) and the oscillation of the excitation pulsed laser 1, (G ) said light detector 5, the high-temperature heating element or the
By the discharge terminal sealed cell 3 is the laser beam passes, the fluorescence spectra of atoms and molecules gas in contact with the hot heating element or the discharge terminal is generated by the reaction is measured, (H) the computer 6 incorporates a theoretical absorption line wavelength of the measurement molecules as data, compares the spectral distribution of the theoretical absorption line wavelength of the measured fluorescence spectrum and the measured molecular, (I) by the computer 6, the grating angle of the tunable laser 2 By controlling the (diffraction angle), the absolute value of the laser wavelength is automatically matched with the optimum excitation wavelength of atoms and molecules with high accuracy. That is, the apparatus of the present invention comprises: (1) In order to set a laser wavelength, a high-temperature heating element such as a ceramic heating element at about 1500 ° C. or a cell 3 in which a discharge terminal is sealed is installed in a laser beam path. . (2) In the cell 3, the gas in contact with the high-temperature heating element or the discharge terminal reacts to generate atoms and molecules for measurement. (3) The wavelength of the laser beam is scanned near the absorption line of the atom / molecule to be measured, the fluorescence generated from the excited atom / molecule is condensed by the lens 4 and detected by the photodetector 5. . (4) By processing the detection signal by the computer 6, the fluorescence spectrum shown in FIG. 5A is measured. (5) Generally, in a wavelength counter attached to a laser device, the absolute accuracy of the wavelength is equal to 0. about 1 nm,
In the laser-induced fluorescence (LIF) method, the wavelength of the laser light must be matched with the wavelength corresponding to the electron energy difference of the measurement molecule with an accuracy of 0.001 nm, and therefore, a deviation occurs between the wavelength counter and the absolute wavelength. In the apparatus according to the present invention, in order to eliminate the deviation between the wavelength counter and the absolute wavelength, the computer 6 is provided with the information shown in FIG.
The theoretical absorption line wavelength of the measurement molecule shown in (b) is stored as data as shown in Table 1, and it is calculated in advance that the wavelength to be set is a '. [Table 1] In Table 1, P1, P2, P21: Q1, Q2, Q12, Q21 representing the name of the absorption line; R1, R2, R12, R21 representing the name of the absorption line; (6) representing the name of the absorption line Measured light (fluorescence) spectrum (abcde)
Is the spectral distribution of the theoretical absorption line wavelength of the measured molecule (a '
b'c'd'e ') is compared with the computer 6 to recognize that the peak value (a) of light (fluorescence) corresponds to the theoretical fluorescence spectrum value (a'). The computer 6 determines that the wavelength is the wavelength of the peak value (a) of the fluorescence intensity. More specifically, the obtained spectrum is corrected as a function of wavelength and signal intensity by adding (+ X) to the wavelength of the experimental value and comparing with the theoretical spectrum, and a value (X) at which the error is minimized is obtained. (A) and (a ') are made to correspond. (7) Based on the determined wavelength, the grating angle (grating angle; diffraction grating angle) of the tunable laser is changed, and the wavelength of the laser light is automatically adjusted by a computer to the optimal excitation wavelength of atoms and molecules to be measured. To match. Therefore, the operation is as follows. (1) Generally, molecules and atoms have specific absorption lines, and the absolute wavelength of the absorption lines is accurately determined with an accuracy of 0.001 nm or more. Therefore, according to the present invention, the absolute wavelength of the laser beam can be obtained with high accuracy. (2) Since the absorption lines of atoms and molecules are used for obtaining the absolute wavelength, there is no influence of the displacement of the optical system or the like, and errors hardly occur. (3) Since atoms and molecules generated by the reaction of gas on the surface of the high-temperature heating element or the discharge area are used,
There is no need to prepare a cylinder or the like, and the apparatus can be made compact and inexpensive. (First Embodiment) FIGS. 1 to 6 show a first embodiment of the present invention. FIG.
1 is a diagram showing an LIF measurement device according to a first embodiment of the present invention. FIG. 2 is an explanatory view of a cell enclosing a high-temperature heating element according to the first embodiment. FIG. 3 is an explanatory diagram of a cell in which a discharge terminal according to the first embodiment is sealed. FIG.
Explanatory drawing of the cell which enclosed the high temperature heating element or discharge terminal which concerns on embodiment. FIG. 5 is a diagram showing a fluorescence spectrum of a molecule according to the first embodiment of the present invention. FIG. 6 is a diagram showing an application example of the present invention to a combustor such as a boiler and a kiln. As shown in FIGS. 1 to 5, a wavelength variable laser 2 is oscillated from a pulse laser 1 for excitation, and a cell 3 in which a high-temperature heating element or a discharge terminal is sealed is set in a laser beam path. The wavelength of the laser beam is scanned near the absorption line of the atoms and molecules generated by the reaction of the gas at the high-temperature heating element or the discharge terminal, and the fluorescence generated from the excited atoms and molecules is scanned by the lens 4. The light is condensed, measured using the light detector 5, and the result is transferred to the computer 6. The spectral distribution of the theoretical absorption line wavelength (a'b'c'd'e ') stored in the computer 6,
The measured fluorescence spectrum (abcde) is compared on the computer 6, and the atoms and atoms calculated by the computer 6 are compared.
The wavelength of the laser corresponding to the optimal excitation wavelength for molecular excitation is calculated, and the grating angle (Grat) of the tunable laser 2 is calculated.
(ing angle; diffraction grating angle), and the computer 6 automatically sets the laser wavelength to the optimum excitation wavelength for the excitation of atoms and molecules for measurement. After the laser beam is formed into a sheet by the beam expander 7, the laser beam is applied to the measuring place 20. Fluorescence generated from the measurement field 20 is collected by the lens 8 and then collected by the CCD.
It is measured by the camera 9. The measurement result is transferred to the computer 6, and the concentration and temperature of the atoms and molecules to be measured are analyzed. The synchronization line 10 synchronizes the oscillation of the excitation pulse laser 1 with the CCD camera 9. As shown in FIG. 1 (b), the apparatus of the present invention is arranged such that the laser beam emitted from the wavelength tunable laser 2 is partially branched by the beam splitter 11 and is incident on the high-temperature heating element enclosure cell 3. Is also possible. A combination of “a molecule or an atom whose absolute wavelength of an absorption line is required with an accuracy of 0.001 nm or more and a device for generating the same,” which can be applied to the present invention,
2 to 4. FIG. 2 is filled with high-temperature heating element 3A in the cell 3, showing the air NO excitation laser wavelength setting device for generating NO molecules by contacting the high temperature heat generating body 3A. FIG. 3 shows a device in which a discharge terminal 3B is incorporated in the cell 3 and air (including water vapor) reacts in a discharge part to generate OH and NO. FIG. 4 shows a device (heating element, discharge terminal, etc.) in which molecules / atoms to be measured such as Na, K, Zn, etc. are sealed in the cell 3 and the temperature is raised to the vaporization temperature of the molecules / atoms. The device to which is added. FIG. 5A shows a measured spectrum, and FIG.
(B) shows the theoretical absorption line wavelength of the measurement molecule. FIG. 6 shows an application example of the present invention to three-dimensional temperature measurement in a combustor 37 such as a boiler or kiln. The wavelengths of the tunable lasers 51 and 52 are set using the laser wavelength setting devices 61 and 62 of the present invention, and the mirrors 33 and 35 and the beam combiner 34 are used to set the wavelength of the boiler, kiln, etc. from the measurement window 36. Combustor 3
7 is incident. The fluorescence generated by the laser light is coaxial with the incident light, and is mirrored by mirrors 35 and 38, lens 39, and filter 4.
The detected temperature is detected by the photodetector 41 using 0 and transferred to the computer 43 via the photodetector controller 42, and the temperature in the combustor 37 is analyzed. [0030] mirror 35 by providing a scanning mechanism, a combustor in a plurality of locations within the 37 by incident laser light, 3 of the combustor 37 by using the principle of laser induced fluorescence (LIF) The dimensional temperature distribution can be measured. Therefore, it is possible to contribute to control of the plant , higher accuracy, and the like. Since the present invention is configured as described above, it has the following effects. (1) According to the present invention, the wavelength of laser light required for two-dimensional and three-dimensional NO concentration measurement such as laser-induced fluorescence (LIF) and temperature measurement is set to the excitation wavelength of atoms and molecules for measurement.
It can be set automatically with high accuracy. (2) By using the present invention, it is possible to make the apparatus compact (for example, 100 × 100 × 200 mm) and inexpensive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an LIF measurement device according to a first embodiment of the present invention. FIG. 2 is an explanatory view of a cell in which a high-temperature heating element according to the first embodiment is sealed. FIG. 3 is an explanatory diagram of a cell in which a discharge terminal according to the first embodiment is sealed. FIG. 4 is an explanatory diagram of a cell in which a high-temperature heating element or a discharge terminal according to the first embodiment is sealed. FIG. 5 is a diagram showing a fluorescence spectrum of a molecule according to the first embodiment of the present invention. FIG. 6 is a diagram showing an application example of the present invention to a combustor such as a boiler and a kiln. FIG. 7 is a diagram showing a conventional wavelength setting device. [Description of Symbols] 1 ... Pulsing laser for excitation 2 ... Tunable laser 3 ... High-temperature heating element or discharge terminal sealed cell 4 ... Lens 5 ... Photodetector 6 ... Computer 7 ... Beam expander 8 ... Lens 9 ... CCD camera 10 ... Synchronous line 11: Beam splitter 20: Measurement field

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01N 21/62-21/74 G01K 11/00-11/30 H01S 3 / 00,3 / 10 JOIS

Claims (1)

(57) [Claims 1] A laser beam is incident on a measurement field, a molecule to be measured is excited at an electron energy level, and light (fluorescence) generated from the excited molecule is measured. in apparatus for performing two-dimensional chemical species concentration measurement and temperature measurement in the measuring field, the excitation pulse laser, a wavelength tunable laser, as well as provided in the order of high-temperature heating element or discharge terminal encapsulated cell, the hot heating element or the discharge terminal and the photodetector the light (fluorescence) input via the lens from encapsulated cell, enter the light (fluorescence) from the high-temperature heating element or the discharge terminal encapsulated cell, the measurement field light (fluorescence) a beam expander for irradiating, input via the lens light (fluorescence) from the measuring field
A CCD camera, a signal from the optical detector receives the signal from the CCD camera, and a computer for outputting the excitation pulse laser, synchronization line for synchronizing the CCD camera and the oscillation of the excitation pulsed laser And the light detector comprises: the high-temperature heating element or the discharge terminal
By laser light in the encapsulated cell passes, the fluorescence spectra of atoms and molecules gas in contact with the hot heating element or the discharge terminal is generated by the reaction is measured and the computer, the theoretical absorption line measurement molecule a built-in wavelength as the data, performs a comparison of the spectral distribution of the theoretical absorption line wavelength of the measured fluorescence spectrum measurement molecule, by the computer, by controlling the grating angle (diffraction angle) of the variable wavelength laser, the laser wavelength A laser wavelength setting device which automatically matches the absolute value of the laser beam to the optimal excitation wavelength of atoms and molecules with high accuracy.