JP2011196832A - Laser type gas analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser type gas analyzer capable of applying desired vibration to an optical part and capable of reducing interference noise originating from a laser beam to enable the measurement of high precision.SOLUTION: In the laser type gas analyzer, a laser element vibration means 28A for finely vibrating a laser element 24 in an optical axis direction is constituted of a straight rod 92, the piezoelectric elements 93 arranged at both ends of the straight rod and fine projections 91 formed in the loop of the standing wave of the straight rod.

Description

  The present invention relates to a gas analyzer that measures a gas concentration by laser light.

  It is known that each gaseous gas molecule has its own light absorption spectrum. Gas analyzers using laser light (hereinafter referred to as “laser-type gas analyzers”) utilize the fact that the absorption amount of laser light at a specific wavelength is proportional to the concentration of the gas to be measured (measurement target gas). It is a device that measures. Gas concentration measurement methods are roughly classified into a frequency modulation method (see Patent Document 1) and a two-wavelength difference method (see Patent Document 2).

  In a laser gas analyzer, interference light is generated due to multiple reflections of light between optical components such as between a laser element and a collimating lens, or between a condenser lens and a light receiving element, due to the coherent nature of the laser light. Then, it is superimposed on the received light signal as interference noise. Since this interference noise fluctuates due to changes in the external environment (particularly temperature), this hinders high sensitivity and high stability of the apparatus.

Therefore, in recent years, a laser type gas detection apparatus provided with means for reducing interference light due to multiple reflection of light between the above-described optical components has been studied (see Patent Document 3).
FIG. 10 shows a laser-type gas detection apparatus described in Patent Document 3. In this laser type gas detection apparatus 700, a light projecting / receiving unit 710 and a reflection unit 720 are opposed to each other in a measurement atmosphere (gas G) with a predetermined measurement optical path length therebetween.

  The light projecting / receiving unit 710 receives and detects the light source unit 730 including a laser element, the condensing lens 740 that condenses the light emitted from the light source unit 730 and passed through the gas, and the light collected by the condensing lens 740. A light receiving element 750A, a light receiving signal processing unit 750B that calculates a gas concentration by processing a light receiving signal detected by the light receiving element 750A, and a vibration unit 760 that slightly vibrates the condenser lens 740 in the optical axis direction. The vibration unit 760 includes various motors such as a vibration motor and a driving unit such as a piezoelectric element, and is directly attached to the condenser lens 740. On the other hand, the reflection unit 720 includes a reflection plate 790 that reflects the laser light from the light projecting / receiving unit 710 toward the measurement atmosphere again.

  The laser light emitted from the light source unit 730 is reflected by the reflection mirrors 770A and 770B, and then emitted from the glass window 780 provided at the center position of the condenser lens 740 toward the measurement atmosphere. The light emitted from the glass window 780 passes through the measurement atmosphere, is reflected by the reflection plate 790, passes through the measurement atmosphere again, is collected by the condenser lens 740, and is received by the light receiving element 750A. The received light is converted into an electrical signal and then subjected to signal processing by the received light signal processing unit 750B.

  In the laser-type gas analyzer 700 configured as described above, when the vibration unit 760 is operated during the gas detection operation, the condenser lens 740 and the window portion 780 in the light projecting / receiving unit 710 vibrate slightly in the optical axis direction. Thus, the distance D1 between the reflection mirror 770B and the window portion 780, the distance D2 between the window portion 780 and the reflection plate 790, the distance D3 between the reflection plate 790 and the condensing lens 740, and the condensing lens 740. And the distance between the optical members such as the distance D4 between the light receiving element 750A and the light receiving element 750A change. As a result, the reflection position of the interference light on the surface of the window portion 780, the surface of the condenser lens 740, and the surface of the reflection plate 790 is changed to cause a phase shift. As a result, the interference light generated at the distances D1 to D4 is averaged during multiple reflection, and interference light unnecessary for measurement can be reduced.

Japanese Patent Laid-Open No. 7-151681 (paragraph [0005], FIG. 4 etc.) JP 2001-235418 A (paragraphs [0012] to [0024], FIG. 2, FIG. 11 etc.) JP 2008-70314 A (paragraph [0020], FIG. 1 etc.)

  As shown in Patent Document 3, the method of minutely vibrating the condenser lens during gas detection is an effective method for reducing interference noise derived from laser light, which is a noise factor that hinders gas concentration measurement. There are the following problems.

  First, in a laser type gas analyzer, since the laser beam is normally expanded and irradiated on the measurement target space, the lens diameter of the condensing lens 740 becomes as large as about 25 to 30 mm. In addition, when measuring the gas concentration in a high temperature and highly corrosive atmosphere such as a flue, it is necessary to use quartz glass having heat resistance and corrosion resistance as a material for the condenser lens 740. The weight of the condensing lens 740 becomes heavier than when a lens is used. In order to vibrate such a large and heavy glass lens, the vibration means 760 also has a large and complicated structure, which causes an increase in cost.

  Further, as shown in FIG. 10, the condenser lens 740 is disposed in a state exposed to the outside of the light projecting / receiving unit 710, and has a structure in which the gas in the flue is directly touched. Usually, the inside of the flue has a negative pressure against the outside air so that the gas does not leak out of the flue. For this reason, when the condensing lens 740 is vibrated, there arises a problem that it becomes difficult to vibrate because the pressure is applied to the condensing lens 740 due to a pressure difference between inside and outside the flue. Although it is conceivable to cover the condensing lens 740 with a glass plate or the like so that the condensing lens 740 is not exposed to the outside, it is difficult to apply since the interference light is further increased by this glass plate.

  Furthermore, when the frequency of the weak vibration is in a high frequency vibration region such as 10 kHz or more, the optical component cannot be regarded as a rigid body, and it is necessary to consider its vibration characteristics (behavior) as an elastic body. For example, when the condensing lens 740 is vibrated at a high frequency, the vibration displacement amount is distributed even on a single condensing lens, which makes it difficult to control the vibration. It was not.

  The present invention has been made in view of the above points, and can provide a desired vibration to an optical component even in a high-frequency vibration region, and can reduce high-precision measurement by reducing interference noise derived from laser light. An object of the present invention is to provide a laser type gas analyzing apparatus.

A gas analyzer according to claim 1 of the present invention provides:
A laser light source unit including a laser element; a laser light emitting optical system that irradiates the gas to be measured with light emitted from the laser element; a condensing optical system that condenses the light transmitted through the gas to be measured; Laser type gas analysis comprising a light receiving element for measuring the intensity of light collected by a condensing optical system, and a vibrating means for minutely vibrating the laser element or at least one of the light receiving elements in the optical axis direction In the device
The vibration means includes
A vibrating portion including a straight rod, piezoelectric elements disposed at both ends of the straight rod, a minute protrusion provided on an antinode of a standing wave of the straight rod, and a vibration control unit that drives the piezoelectric element. Prepared,
The laser element or the light receiving element is vibrated through the minute protrusions by exciting the straight bar.

A gas analyzer according to claim 2 of the present invention is the gas analyzer according to claim 1,
The first and second straight bars, first and second minute protrusions provided on the antinodes of the standing waves of the first and second straight bars, respectively, and a pedestal, and the first minute While the protrusion is attached to the laser element or the light receiving element, the second minute protrusion is attached to the pedestal.

The gas analyzer according to claim 3 of the present invention is the gas analyzer according to claim 1,
A set of two piezoelectric elements that expands and contracts in the length direction is configured as a bimorph type vibration part that is bonded to the straight rod, and the minute protrusions are attached to the laser element or the light receiving element. It is characterized by.

  A gas analyzer according to claim 4 of the present invention is characterized in that, in any one of claims 1 to 3, a vibration in a primary mode or a tertiary mode is induced in the straight bar.

  In the laser type gas analyzer of the present invention, the interference noise derived from the laser beam is reduced by minutely vibrating at least one of the laser element and the light receiving element in the optical axis direction using the vibrating means. These laser elements and light receiving elements constituting the optical system are parts that are much smaller and lighter than the condenser lens. Therefore, according to the laser type gas analyzer of the present invention, a more reliable gas analyzer can be provided as compared with the case where a large and heavy condenser lens is vibrated. Furthermore, since these optical components are vibrated through the minute protrusions, desired vibration can be given even in a high frequency vibration region, and gas concentration analysis can be performed with high accuracy.

FIG. 1 is a schematic cross-sectional view showing the overall configuration of the laser type gas analyzer of the present embodiment. FIG. 2 is a diagram showing a schematic configuration of the laser light source section shown in FIG. FIG. 3 is a diagram showing a scanning signal waveform of the laser type gas analyzer shown in FIG. FIG. 4 is a diagram showing a schematic configuration of the received light signal processing unit shown in FIG. FIG. 5 is a diagram showing a wavelength scanning signal component extracted by the received light signal processing unit of the laser gas analyzer shown in FIG. 1, and shows a waveform when a gas is detected. FIG. 6 is a diagram showing a first embodiment of the vibration means. FIG. 7 is a diagram illustrating an example of a signal waveform when there is no vibration and a signal waveform when there is vibration. FIG. 8 is a diagram showing a second embodiment of the vibration means. FIG. 9 is a diagram showing a third embodiment of the vibration means. FIG. 10 is a diagram showing a configuration of a conventional laser gas analyzer equipped with a vibrating means for minutely vibrating the condenser lens.

  Exemplary embodiments of a laser type gas analyzer according to the present invention will be described in detail with reference to the accompanying drawings. In the following, an example in which the present invention is applied to a laser gas analyzer using a frequency modulation method will be described.

  FIG. 1 is a schematic cross-sectional view showing a configuration of a laser type gas analyzer 10 of the present embodiment. A laser type gas analyzer 10 illustrated in FIG. 1 is installed on walls W1 and W2 of a pipe such as a flue through which a gas to be measured G (not shown: hereinafter referred to as “gas G”) passes. Has been. The laser gas analyzer 10 includes a pair of flanges 11a and 11b, covers 13 and 14 attached to the flanges 11a and 11b, a laser light source unit (laser light source unit) 20 accommodated in one cover 13, and A collimating lens (laser beam emitting optical system) 30, a condensing lens (condensing optical system) 40 accommodated in the other cover 14, a light receiving element 50, and a light receiving signal processing unit 60 are configured.

  The pair of flanges 11a and 11b are formed in a cylindrical shape with both ends opened, and are fixed to the flue walls W1 and W2 by welding or the like. The covers 13 and 14 are formed in a bottomed cylindrical shape with one end opened and the other end closed, and are attached to the flanges 11a and 11b via attachment seats 12a and 12b, respectively.

  Light emitted from the laser light source unit 20 disposed in the cover 13 is collimated into parallel light L by an optical system including a collimating lens 30 and enters the gas G in the flue. The parallel light L is absorbed by the gas when passing through the gas G in the flue. The parallel light L that has passed through the flue is collected by the condenser lens 40 disposed in the cover 14, then received by the light receiving unit 50, and detected as an electrical signal by the light reception signal processing unit 60.

  FIG. 2 is a diagram showing a schematic configuration of the laser light source unit 20 shown in FIG. The laser light source unit 20 is configured as a unit in which a plurality of components such as a laser element 24 described below are accommodated in a package. As shown in FIG. 2, inside the package of the laser light source unit 20, a wavelength scanning drive signal generation unit (wavelength scanning signal generation unit) 21 and a high frequency modulation signal generation unit (frequency modulation unit) 22 as wavelength control units, A current control unit (laser element driving unit) 23, a laser element 24, a thermistor 25, a Peltier element 26, a temperature control unit 27, a laser element oscillation unit 28, and a vibration control unit 29 are accommodated.

  The wavelength scanning drive signal generator 21 generates a wavelength scanning signal that makes the emission wavelength of the laser element 24 variable so as to scan the absorption wavelength of the gas G. The high-frequency modulation signal generator 22 generates a sine wave signal of, for example, about 10 kHz and frequency-modulates the wavelength in order to detect the gas absorption waveform. The current control unit 23 generates a signal (laser drive signal) obtained by combining the wavelength scanning signal generated by the wavelength scanning drive signal generation unit 21 and the sine wave signal generated by the high frequency modulation signal generation unit 22. The laser element 24 is driven by converting into drive current.

  The laser element 24 is a semiconductor laser (LD: laser diode), and emits laser light by a drive current supplied from the current control unit 23. The thermistor 25 is a temperature detection element for detecting the temperature of the laser element 24, and is disposed in contact with the laser element 24. The Peltier element 26 is a heating / cooling means for the laser element 24 and is disposed in contact with the thermistor 25. The temperature control unit 27 controls the Peltier element 26 based on the temperature measured by the thermistor 25, and thereby maintains the temperature of the laser element 24 at a constant temperature, thereby controlling the oscillation wavelength of the laser light.

  The laser element 24, thermistor 25, and Peltier element 26 described above are arranged in a stacked and integrated state inside the package of the laser light source unit 20 as shown in FIG. Laser element vibration means 28 is provided so as to be in contact with the Peltier element 26.

  The laser element vibration means 28 vibrates the laser element 24 together with the Peltier element 26 and the thermistor 25 in the optical axis direction of the laser light by vibrating itself when driven. By this laser element vibration means 28, the distance between the laser element 24 and the collimating lens 30 can be changed.

  Since the laser element 24 is a very small package having a total length of about 5 mm, a small and inexpensive laser element vibration means 28 can be used. Specifically, a piezoelectric element or the like can be employed as the laser element vibration unit 28. The laser element vibration means 28 is controlled based on a signal from the vibration control unit 29. The specific structure of the laser element vibration means 28 and details of the vibration control unit 29 will be described later.

  As shown in FIG. 3, the output signal generated by the wavelength scanning drive signal generator 21 in FIG. 2 has a trapezoidal shape that is repeated at a constant period. The signal S1 in FIG. 3 is a part that linearly changes the magnitude of the current supplied to the laser element 24 via the current control unit 23. With this signal S1, the emission wavelength of the laser element 240 is gradually shifted. For example, in the case of ammonia gas, a line width of about 0.2 nm can be scanned.

  The signal S2 shown in FIG. 3 is a portion that does not scan the absorption wavelength but causes the laser element 24 to emit light, and is set to a value equal to or higher than a threshold current value at which the light emission of the laser element 24 is stabilized. Further, the signal S3 is a portion where the drive current is substantially zero.

  Further, the wavelength scanning drive signal generator 21 generates a pulse-like trigger signal (not shown) synchronized with one period of the wavelength scanning signal, and performs an arithmetic processing for detecting the gas concentration using the trigger signal. It transmits to the part 65 (refer FIG. 4). For example, the trigger signal is generated in synchronization with the timing of the wavelength scanning drive signal (the generation timing of the signal S3) that makes the drive current of the laser element 24 zero.

  FIG. 4 is a diagram showing a schematic configuration of the light receiving element 50 and the received light signal processing unit 60 in FIG. The light receiving element 50 is, for example, a photodiode, and an element having sensitivity to the emission wavelength of the laser element 24 is applied. The output of the light receiving element 50 is sent to the received light signal processing unit 60, converted into a voltage output by the IV converter 61, and a high frequency noise component is removed by the low pass filter 64A. The output signal from the low-pass filter 64A is input to the synchronous detection circuit 63 to which the 2f signal (double wave signal) from the oscillator 62 is added, and only the amplitude of the double frequency component of the modulation signal of the laser beam is extracted. The output signal of the synchronous detection circuit 63 is subjected to noise removal and amplification by the low-pass filter 64B, and is sent to the arithmetic unit 65. The calculation unit 65 performs calculation processing for gas concentration detection.

  A concentration measurement method using the laser gas analyzer 10 configured as described above will be described. First, the temperature of the laser element 24 is detected by the thermistor 25 in advance. Further, the temperature control unit 27 controls the energization of the Peltier element 26 so that the temperature of the laser element 24 is maintained at a desired temperature so that the gas G can be measured at the central portion of the wavelength scanning drive signal S1 shown in FIG.

  The laser element 24 is driven by changing the drive current while keeping the temperature of the laser element 24 at a desired temperature, and the light is emitted from the laser element 24 toward the flue where the gas exists, and the light is transmitted to the light receiving element 50. Is incident. When the laser beam is absorbed by the gas, the second harmonic signal is detected by the synchronous detection circuit 63, and an absorption waveform of the gas appears. FIG. 5 is a graph showing a waveform when gas is detected. A signal 81 is a received light signal waveform output from the IV converter 61, and a signal 82 is an output waveform of the synchronous detection circuit 63. . In the output waveform of the synchronous detection circuit 63, a portion A surrounded by a dotted line is a gas absorption waveform.

Since the magnitude of the absorption waveform A becomes the gas concentration, the magnitude of the maximum value or the minimum value of the absorption waveform A may be measured, or the signal change may be integrated. However, when an offset variation occurs in the output of the synchronous detection circuit 63 for some reason, an error occurs in detection of only the maximum value or minimum value or detection by integration, and there is a possibility that the gas concentration cannot be detected accurately. Therefore, in order to detect the gas concentration with higher accuracy and stability, as shown in the following equations (Equation 1) and (Equation 2), the maximum value (point C in FIG. 5) and the minimum value (in FIG. 5). It is preferable to take the difference between the B point and the D point), calculate the absolute value of the difference value, and detect the gas concentration.
(Equation 1)
Gas concentration = α × | BC
(Equation 2)
Gas concentration = α × | C−D |
In the equations (1) and (2), C represents the maximum value in the absorption waveform A in FIG. 5, B and D represent the minimum values in the absorption waveform A, and α represents the gas concentration conversion coefficient.

  On the other hand, when there is no gas absorption, since the double frequency signal is not detected in the synchronous detection circuit 63, the output of the synchronous detection circuit 63 is ideally a straight line.

  Although the gas concentration can be detected by the above-described method, since the laser element 24 is used as a light source, for example, between the laser element 24 and the collimating lens 30 and between the condenser lens 40 and the like due to its extremely high coherence. A part of the laser light is multiple-reflected between the light-receiving element 50 and this multiple-reflected light becomes interference light.

  In order to reduce this interference noise, the laser element vibration means 28 described above causes the laser element 24 to vibrate slightly in the optical axis direction, thereby changing the distance between the laser element 24 and the collimating lens 30. The laser element vibration means 28 is configured using a piezoelectric element, and vibrates at a vibration frequency and amplitude (a displacement amount in the optical axis direction) based on a command signal from the vibration control unit 29. The amplitude of the laser element vibration means 28 is several μm to several tens of μm, and the amplitude is preferably constant regardless of time. Further, the vibration frequency of the laser element vibration means 28 is set to 10 times (for example, 100 kHz or more) or 1/10 times (for example, 1 kHz) or more of the frequency (for example, 10 kHz) of the sine wave signal generated by the high frequency modulation signal generator 22. I want to see that. When the vibration frequency of the laser element vibration means 28 is greater than 1/10 times and less than 10 times the frequency of the sine wave signal, it is difficult to separate the laser modulation frequency (for example, 10 kHz) from the vibration frequency, and it is difficult to remove interference noise. It becomes.

  When the laser element 24 is vibrated by the laser element vibration means 28 described above, the distance between the laser element 24 and the collimating lens 30 changes. As a result, the intensity of the interference light generated by the multiple reflected light between the surface of the collimator lens 30 and the laser element 24 varies because the interference generation condition changes. The period of the interference light fluctuation is equal to the vibration frequency of the laser element 24. Therefore, it is possible to remove interference noise from the detection signal by filter processing such as a low-pass filter that can remove the vibration frequency component.

Next, a specific configuration of the laser element vibration unit will be described.
FIGS. 6A and 6B are diagrams showing a first embodiment of the laser element vibration unit. FIG. 6A shows a vibration state in the first-order mode, and FIG. 6B shows a vibration state in the third-order mode. .
The laser element vibration means 28A includes a vibration unit 90A using a piezoelectric element and a vibration control unit 29. The vibration unit 90A includes a straight bar 92, a pair of piezoelectric elements 93 disposed at both ends of the straight bar 92, and a base 94 that supports them. The piezoelectric element 93 and the straight bar 92 are fixed with an adhesive.

  A minute projection 91 is provided at the center of the straight rod 92 in the length direction (antinode of standing wave vibration), and the laser element 24 is attached to the straight rod 92 via the minute projection 91. When the laser element 24 is attached, if the laser element 31 touches a portion of the straight bar 92 that vibrates in a direction other than the optical axis direction, the optical axis may be shifted. Further, it is difficult to perform a positioning operation for matching the center point of vibration with the mounting position of the laser element 24. By providing the minute protrusion 91 between the laser element 24 and the straight rod 92 as in the present embodiment, the laser element 24 can be vibrated accurately in the direction of the optical axis, and positioning at the time of attachment is also possible. It becomes easy. In addition, the vibration characteristics can be finely adjusted by changing the size of the minute protrusion 91 that is an additional mass of the vibration system.

  When the two piezoelectric elements 93 are driven at the same frequency and the same phase, a standing wave flexural vibration is induced in the straight bar 92. Any vibration mode may be used as long as the center of the straight bar 92 is an odd-order vibration mode that is likely to induce vibration, and in order to give a large vibration displacement to the laser element 24, FIG. A primary or tertiary mode as shown in FIG.

  FIG. 7 shows an example of an output signal waveform by the received light signal processing unit when the laser element vibration unit 28A is operated and not operated. As shown in FIG. 7, uneven signal interference noise is generated in the signal waveform when the laser element vibration means 28A is not operated (no vibration). On the other hand, it can be seen that when the laser element vibration means 28A is operated (with vibration), the interference noise can be greatly reduced.

8A and 8B are diagrams showing a second embodiment of the laser element vibration means. FIG. 8A shows the vibration state in the first-order mode, and FIG. 8B shows the vibration state in the third-order mode. .
In this laser element vibration means 28B, a displacement increasing mechanism using two straight bars is used, and other configurations are the same as those in the first embodiment. The vibration unit 90B includes a first straight bar 92 and a second straight bar 96, and piezoelectric elements 93 are disposed at both ends of the opposed straight bars. In addition, a first microprojection 91 and a second microprojection 95 are provided at the center in the length direction of the first and second straight bars (the antinode of standing wave vibration), respectively. The first microprojection 91 is attached to the laser element 24, while the second microprojection 95 is attached to the pedestal 94. Here, when the piezoelectric elements 93 at both ends are driven, the first microprojection 91 and the second microprojection 95 vibrate so as to approach and separate from each other in opposite directions. According to this embodiment, as compared with the first embodiment described above, even when the voltage applied to the piezoelectric element 93 is the same, the vibration displacement can be given to the laser element 24 twice.

FIG. 9 shows a third embodiment of the laser element vibration means.
In this laser element vibration means 28C, the vibration part 90C has a bimorph configuration. That is, the straight bar 92 is a doubly-supported beam whose both ends are fixed to the inner wall of the laser light source case (not shown). Four sheets are attached. Similarly to the above-described embodiment, a minute protrusion 91 is provided at the center in the length direction of the straight bar 92 (antinode of standing wave vibration), and the laser element 21 is attached via the minute protrusion 91. When the piezoelectric element 97 is driven, the piezoelectric element 97 expands and contracts along the length direction, causing the straight bar 92 to bend and vibrate. According to this embodiment, a large vibration displacement can be obtained even with a single straight bar.

By the way, the most interference light is generated between the laser element 24 and the collimating lens 30. Therefore, the interference noise is greatly reduced by vibrating the laser element 28 as described above, and the gas concentration can be measured more accurately than before.
However, the interference light is also generated between the condenser lens 40 and the light receiving element 50. Therefore, a light receiving element vibrating means (not shown) for vibrating the light receiving element 50 may be provided. The light receiving element vibration means is configured in the same manner as the laser element vibration means 28 and is disposed in contact with the light receiving element 50.

In the above embodiment, the laser gas analyzer using the frequency modulation method as the gas concentration measurement method has been described. However, the present invention is not limited to this, and the absorption amount of the laser beam at a specific wavelength is described. Can be applied to a laser gas analyzer using another method for measuring the gas concentration by utilizing the fact that is proportional to the concentration of the gas to be measured.
For example, a laser beam having two wavelengths, a wavelength that is easily absorbed (large absorption) and a wavelength that is difficult to absorb (small absorption), is irradiated from the laser element to the measurement gas. The same effects as those described above can also be obtained in a laser type gas analyzer using a two-wavelength difference method in which a gas concentration is received by a light receiving element.

DESCRIPTION OF SYMBOLS 10 Laser type gas analyzer 11a, 11b Flange 12a, 12b Mounting seat 13, 14 Cover 20 Laser light source part 21 Wavelength scanning drive vibration generation part (wavelength scanning signal generation means: wavelength control means)
22 High frequency modulation signal generator (frequency modulation means: wavelength control means)
23 Current controller (laser element driving means)
Reference Signs List 24 Laser element 25 Thermistor 26 Peltier element 27 Temperature control unit 28A, 28B, 28C Laser element oscillation means 29 Vibration control unit 30 Collimator lens (laser beam emission optical system)
40 Condensing lens (Condensing optical system)
50 Light Receiving Element 60 Light Receiving Signal Processing Unit 61 I / V Converter 62 Transmitter 63 Synchronous Detection Circuit (Double Frequency Component Detection Means)
64A, 64B Low-pass filter 65 Arithmetic unit 91, 95 Micro projection 92, 96 Straight bar G Gas to be measured L Parallel light (laser beam)
W1, W2 (in the flue) walls

Claims (4)

A laser light source unit including a laser element;
A laser beam emission optical system for irradiating a gas to be measured with light emitted from the laser element;
A condensing optical system for condensing the light transmitted through the measurement gas;
A light receiving element for measuring the intensity of the light collected by the condensing optical system;
In a laser type gas analyzer comprising a vibrating means for minutely vibrating at least one of the laser element or the light receiving element in the optical axis direction,
The vibration means includes
A vibrating portion including a straight rod, piezoelectric elements disposed at both ends of the straight rod, a minute protrusion provided on an antinode of a standing wave of the straight rod, and a vibration control unit that drives the piezoelectric element. Prepared,
A laser type gas analyzer characterized in that the laser element or the light receiving element is vibrated through the minute projections by exciting the straight bar. The vibrating part is composed of first and second straight bars, first and second minute protrusions provided on the antinodes of standing waves of the first and second straight bars, and a pedestal, respectively.
2. The laser gas analyzer according to claim 1, wherein the first minute protrusion is attached to the laser element or the light receiving element, and the second minute protrusion is attached to the pedestal. .   The vibrating part is configured as a bimorph type vibrating part formed by sticking a set of two piezoelectric elements extending and contracting in the length direction to the straight rod, and the minute protrusion is attached to the laser element or the light receiving element. The laser gas analyzer according to claim 1, wherein the laser gas analyzer is attached. The laser gas analyzer according to any one of claims 1 to 3, wherein vibration of a primary mode or a tertiary mode is induced in the straight rod.