JPH03200026A - Cars reference light measuring instrument - Google Patents

Abstract

PURPOSE:To enhance the accuracy of the temp. measurement of gas by providing a dichroic filter removably and insertably from and into an optical path for the light which is reflected by a dichroic mirror and enters an optical fiber. CONSTITUTION:Gaseous Ar 13b is injected from an Ar gas injecting nozzle 13a and the gaseous nitrogen molecules desired to be measured are purged so that the gas 13b is filled as the atmosphere in a test section 13 where the measuring point 12 to be condensed with pumping light 7 and Stockes light 8 outputted by dye lasers 5, 6 exists. The dichroic filter 17 is removed from the optical path. The non-reconant coherent and non-Stokes Raman diffused (CARS) light is generated from the gas 13b when the pumping light 7 and the Stokes light 8 are condensed to the measuring point 12. This light and the two laser beams are made incident via a lens 14 on the dichroic mirror 15, by which the beams are separated to the reflected light 16 and the transmitted laser beams 7, 8. The slight laser beams 7, 8 remain in this light 16 and the laser beams are condensed to an end face 20a, from which the beams enter the optical fiber 20. The beams are then introduced to a spectroscope 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention applies to CAR8 (coherent non-Stokes Raman diffusion; hereinafter referred to as CAR8) which is applied to the measurement of gas temperature such as combustion gas in various burners and engine cylinders. )Reference light measurement device.

[Conventional technology]

A conventional device is shown in FIG.

In Fig. 5, a laser beam 2 oscillated from an excimer laser 1 is split into two by a half mirror 3 and a total reflection mirror 4, each of which excites a dye laser 5. , oscillates the town's laser light.

Here, the laser beam with a wave number W is pumped with a 7° wave number W.
The laser light of s is called Stokes light 8.

Difference between wave number Ws of Stokes light 8 and wave number wp of pump light 7'! 1; L where lp -'Ias is equal to the vibrational energy level difference (difference in energy between the ground level and the first excited level) of the gas molecule to be measured (in this case, nitrogen molecules)
It has been adjusted accordingly.

The pumping light 7 and the Stokes light 8Fi are combined into one by a dichroic mirror 9 and a total reflection mirror 10 that reflect only the light with a certain wave number and pass the other wave numbers, and are combined into one by the lens 11 at the measurement point. The light is focused on 12.

The space including the measurement points 2 is called a test section 13.

Because the gas molecules present there generate CaH2 light, which is the third light, this C
The aH2 light passes through the lens 14 along with two other laser beams 7°8.
The dichroic mirror 15 separates the parallel light into reflected light 16 and transmitted laser light 7 and 8.

Reflected by the dichroic mirror 15, the CaH8 light and a very small amount of the laser beam 7.8 remain in the nine beams 16, and the dichroic mirror 15a is used to separate the CaH2 light and the laser beam. .

The separated 7IcCAR8 light 18 enters one end of the optical fiber 20 through a lens 19t, and is emitted from the other end of the optical fiber 20 located away from the entrance.
The AR8t18 is guided to a spectrometer 22 by a lens 21.

The CaH2 light separated by the spectrometer is converted into voltage by the photoelectric converter 23, and a spectral waveform is obtained by the signal processor 24.

This spectral waveform includes the wavelength characteristics of the laser beam and the sensitivity characteristics of the light receiving side, so it is necessary to correct them, and the non-resonant CaB6 light from Ar gas is used as a reference for correction. Used as light.

In order to obtain a reference light used for correction of this CaH2 light, a non-resonant C
An accurate CARS spectrum can be obtained by filling the container with Ar gas that generates aB6 light, inserting this container into the test section, obtaining the spectrum waveform in the same way, and taking the intensity ratio of the CaH2 light and the reference light.

The spectral waveform obtained in this way is shown in Figure 4, and it is compared with the theoretically calculated spectral waveform shown in the third table in sequence, and the temperature of the theoretical spectrum that shows the best A match is determined. The temperature at the measurement point is determined.

[Problem to be solved by the invention]

The reference light produced by Ar gas at about atmospheric pressure used in the conventional setup is the CA of the gas molecules to be measured.
Since the intensity is lower than that of RS light, Ar
The intensity is increased by increasing the gas pressure or increasing the output of the laser beam, but the energy intensity becomes too large and the Ar gas causes dielectric breakdown inside the container, causing a discharge phenomenon and causing noise. This may cause damage to the window glass.

Friend, depending on the structure of the specimen to be measured, there are many cases where it is not possible to fill the test section with Ar gas and insert a fixed container, or to seal the Ar gas under pressure.

The present invention seeks to solve the above problems.

[Means for Solving Problem a] The CAR8 reference light measurement device of the present invention generates two types of laser beams with different wave numbers, and measures the vibrational energy level of gas molecules to measure the difference in wave numbers between the two laser beams. According to the difference, the light is focused on the space where the above gas exists and generates CaH2 light,
The light containing the same CAR8 light is input to a dichroic mirror to separate the CaH2 light, and the same CAR8 light is passed through an optical fiber and a spectrometer to a photoelectric converter, where it is photoelectrically converted and converted into a Yuden signal. Input into the processor to generate gas molecules CaH8
Analyzing the spectrum of light and determining the difference in the spectral waveform
It is characterized by comprising a guichroic filter that can be inserted into and removed from the optical path of the zero-harm light that enters the AIPAR, and a means for discharging Ar gas into the space where the two laser beams are focused. .

[Effect]

In the above, when measuring all of the CAR3 light generated by gas molecules, a dichroic filter is inserted in the optical path, two lasers are focused on the space where gas molecules exist to generate CARS light, and a dichroic filter is inserted into the optical path to generate CARS light. A mirror reflects and separates the CARS light, and the CARS8 light is further filtered through a microchroic filter to remove a small amount of the remaining laser light.After that, the optical fiber, spectrometer, and photoelectric converter1! r: The signal is then converted into an electrical signal, and a spectral waveform is obtained by a signal processor.

Next, when obtaining a reference light, the guichroic filter is removed from the optical path, and Ar gas is discharged into the space where the two laser beams are focused to purge the gas molecules. shall be.

In the above state, in the space where the two laser beams are incident, A
Non-resonant CARS light is generated by the r gas, and the dichroic mirror reflects the non-resonant CARS light containing a small amount of laser light and enters the optical fiber.

A high-intensity non-resonant CARS light is obtained by the above-mentioned small amount of laser light being incident on the end face of the optical fiber, and this non-resonant CARS light is incident on a photoelectric converter via a spectroscope and is converted into an electrical signal. A spectral waveform of non-resonant CARS light, which is a reference light, is obtained by a signal processor.

The CARS light is corrected by a reference light to measure the temperature of the gas molecules, but the reference light does not contain the CARS light because the gas molecules have been purged with Ar gas, and the reference light does not contain the CARS light, and the reference light does not contain the CARS light because the gas molecules have been purged with Ar gas. Since a high-intensity non-resonant CARS beam is obtained that is applied to the end face of the beam, the CARS spectrum corrected by the reference beam becomes more accurate.
Highly accurate gas temperature can be obtained.

As a result of the above, the sealed container for AI/gas used in conventional equipment is no longer required, eliminating the risk of dielectric breakdown or damage, and making it possible to perform measurements at 1A locations where the container cannot be inserted. Since a reference light with high intensity and low noise can be obtained, it has become possible to improve the accuracy of gas temperature measurement.

〔Example〕

An embodiment of the present invention is shown in FIG.

In this embodiment shown in FIG. 1, a laser beam 2 outputted from an excimer laser 1 enters a half mirror 3, and the half mirror 3 reflects a part of the laser beam 2 and transmits and reflects the rest. The laser light enters the dichroic mirror 9 via the dye laser 5 and is reflected, and the transmitted laser light is reflected by the total reflection mirror 4 and enters the dye laser 6, which emits Stokes light 8. Output and total reflection mirror 1
The Stokes light 8 that is incident on 0 and reflected by the total reflection mirror 10 passes through the dichroic mirror 9, is combined with the bombing light 7 reflected from the dichroic mirror 91C, and then passes through the lens 11. The nitrogen gas that is focused and measured on the measurement point 12 of the test section 13 generates CARS light, and the CARS light is transmitted together with the laser light to the dichroic mirror 15i via the lens 14.
The dichroic mirror 15 transmits most of the laser light and reflects the light 1 and 6 f, which are made up of part of the laser light and the CARS light, and the reflected light 16 is passed through the lens 19 and the optical fiber 20. ．． In the CAR8 reference light measuring device, the signal is inputted to the spectrometer 22 via the lens 21', converted into an electrical signal by the optical gravity converter 23Vcj, and inputted to the signal processor 24, reflected by the dichroic mirror +5, and converted to 7'CCAR8. A dichroic film 17 is inserted into and taken out from the optical path of the light 16, which is a part of the laser beam, and an arm-shaped nozzle 13a is installed in the test section 13 to eject Ar gas. There is.

In this example, CAR generated by 9 elementary gas molecules
When determining S-1'e at 6 rivers, the CARS light and two laser lights are reflected by the dichroic mirror 15, trench fc)
Since the process up to the point of transmission is the same as the conventional one, a complete explanation of its operation will be omitted.

In the above, when measuring the CARS light, the CARS light reflected from the dichroic mirror 15 and the light 16, which is a very small amount of laser light, enter the gichroic filter 17 installed at right angles to the optical path, and are converted into CARS light. After passing through the filter, the laser beam is reflected and removed.

The separated 7'cCAR8 light 18 is guided to the optical spectrometer 22#C through the lens 19.21 and the optical fiber 20, as in the conventional case, and photoelectrically converted by the photoelectric converter 23 to the signal processor 2.
4, a 1x vector waveform is obtained.

Next, when obtaining a reference light, the test section 131d has the measurement point 12 where the bombing light 7 and the Stokes light 8 outputted by the dye lasers 5 and 6 are focused, and the Ar gas ejector 3b is ejected from the Ar gas injection nozzle 13a. The nitrogen gas molecules that are injected and to be measured are purged to create an atmosphere of gas 13b, and are removed through the optical path filter 17rt.

When the bombing light 7 and the Stokes light 8 are focused on the measurement point 12, % Ar gas 13b17C, C non-resonant CA
R8 light is generated, and this CAR8 light and two laser beams enter the dichroic mirror 15 through the lens 14.
The laser beams are separated into reflected light 16 and transmitted laser beams 7 and 8. A small amount of laser beams 7 and 8 remain in the light 16 reflected by the dichroic mirror 15, and this laser beam is focused on the end surface 20a via the lens 19.
Light 7 enters the eyeglass 20.

When the laser beams 7 and 8 enter the optical fiber 20,
Since the generated non-resonant CAR8 light is proportional to the square of the density of molecules, the above laser light has a very high density compared to gas.
8 lights are generated, guided to a spectroscope 22, photoelectrically converted by a photoelectric converter 23, and a spectral waveform of a reference light is obtained by a signal processor 24.

At the measurement point r2Vc, the nitrogen gas to be measured is completely purged by the Ar gas 13blC, and a reference light that does not contain the CAR3 light of the nitrogen gas molecules to be measured is obtained, and it is also focused on the end face 20a of the optical fiber 20. Since the emitted laser beam generates a non-resonant CAR8 beam through the optical fiber 20, the intensity of the reference beam is greatly increased compared to the conventional device Tl1tT/c, as shown in FIG.

The above reference light is a CAR generated from gas molecules to be measured.
The CARS spectrum, which does not include the 8 light and has a higher intensity, has the wavelength characteristics and sensitivity characteristics corrected by taking the intensity ratio with the CAR 8 light, and is more accurate, and is more in line with the theoretical spectrum waveform. By comparison, the temperature at the measurement point 12 can be determined with high accuracy.

The above-mentioned method eliminates the need for a sealed 5-liter A1 gas container when used with the conventional device, eliminating the risk of insulation breakdown or damage, and making it possible to perform measurements in locations where the container cannot be inserted. Since reference light with high intensity and low noise can be obtained, it has become possible to improve the accuracy of temperature measurement.

〔Effect of the invention〕

In the CAR8 reference light measuring device of the present invention, when obtaining the reference light, the space where the two laser beams are focused is purged with Ar gas, and the light from the same space is provided in the optical path of the reflected light of the dichroic mirror that is incident. By removing the dichroic filter and generating non-resonant CAR8 light incident on the end face of the optical fiber using a small amount of laser light, the sealed container for fcAr gas used in conventional equipment is no longer required. This eliminates the risk of edge breakage or damage, making it possible to perform measurements in locations where the container cannot be inserted, and providing a reference light with high intensity and low noise, making it possible to improve the accuracy of gas temperature measurements. It became.

[Brief explanation of drawings]

The first south diagram is an explanatory diagram of an embodiment of the present invention, and the second diagram is a comparison diagram of the reference light according to the above embodiment with that of a conventional device.
Figure 3 is a spectrogram obtained by theoretical calculations, and Figure 4 is an experimental spectral diagram. Gas CARS Spectrum 4. FIG. 5 is an explanatory diagram of a conventional apparatus. 1... Excimer laser, 2... Excimer laser light, 3... Half mirror 14... Total reflection mirror 5.
... Dye laser, 6... Dye laser, 7... Bumping light, 8... Stokes light, 9... Dichroic mirror lO... Total reflection mirror Jl... Lens 112.
...i 111 points, 13...test section,
13a...Ar gas injection nozzle, 13b...Ar
Gas 14...Lens, 15...Dichroic mirror l6, 013...Reflected light, 17...Dichroic filter 1
8...CAR8 light, Engineering 9...lens,...light 7 eyeper, 20a...end face,...lens,
22... Spectrometer,... Photoelectric converter, 24... Signal processor.

Claims (1)

[Claims] generating two types of laser beams with different wave numbers, and measuring the wave number difference between the two laser beams; focusing the light on a space where the gas exists in accordance with the vibrational energy level difference of gas molecules to generate curse light; Light containing the cursed light is input to a dichroic mirror to separate the cursed light, the cursed light is inputted to a photoelectric converter via an optical fiber and a spectrometer, and the photoelectrically converted electrical signal is input to a signal processor. In a curse reference light measurement device that analyzes the spectra of gas molecule curse light and measures gas temperature from differences in spectral waveforms, a curve reference light measuring device is provided that can be inserted into and taken out of the optical path of the light that is reflected by the dichroic mirror and enters the optical fiber. A curse reference light measurement device comprising: a dichroic filter; and means for discharging argon gas into a space where the two laser beams are focused.