JP3425232B2 - Current meter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a velocity meter for measuring the velocity of fine particles in a fluid to be measured using a laser beam and outputting this velocity as the fluid velocity to be measured. The present invention relates to a velocity meter which is small in size, easy to move, easy and easy to perform accurate measurement, and is capable of obtaining information on a flow direction.

[0002]

2. Description of the Related Art Conventionally, for example, a Pitot tube or a hot wire anemometer has been widely used as a means for measuring the flow velocity of a fluid to be measured. In particular, recently, an anemometer using a gas laser or a semiconductor laser as a light source has been used. Is becoming available.

FIG. 9 is a schematic diagram showing a configuration example of a conventional anemometer using this type of laser light. In FIG. 9, the anemometer has a gas laser 1 that emits laser light as a light source. The laser light from the gas laser 1 is split into two parallel laser lights by a beam splitter 2 and is collected by a focus lens 3. It is illuminated and forms interference fringes in the measurement area 4. The direction of the confusion light reflected from the fine particles 6 contained in the fluid to be measured 5 flowing in the measurement region 4 is changed by the mirror 7, and the scattered light is condensed by the lens 8 and collected. The emitted light is received by the photomultiplier tube 9, and the photomultiplier tube 9 outputs an electric signal corresponding thereto. The output of the photomultiplier tube 9 is calculated by the signal processing unit 10.

In the conventional anemometer constructed as above, interference fringes are formed in the measurement region 4 by the two laser beams having the same intensity and the same phase divided by the beam slitter 2.

By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 present in the fluid to be measured 5 are also
It passes through the measurement area 4, that is, the interference fringes, at the same speed. Then, when passing through the interference fringes, the fine particles 6 emit scattered light that changes in intensity depending on the interference fringes. This scattered light is condensed on the photomultiplier tube 9 through the lens 8. Then, the photomultiplier tube 9 outputs a signal according to the scattered light that changes strongly, that is, a Doppler signal, to the signal processing unit 1.
Output to 0.

In the signal processing unit 10, based on the known interval of interference fringes and the time of Doppler signal,
The velocity in the direction perpendicular to the interference fringes of the particles 6 is calculated. Since the calculated velocity is also the flow velocity of the fluid to be measured 5 that flows at the same velocity as the fine particles 6, by arranging the measurement region 4 in advance so that the interference fringes are vertical in the flowing direction of the fluid to be measured 5, The speed of the fluid to be measured 5 can be measured.

However, since the optical system of the laser Doppler velocimeter as described above is of the backscattering type, the amount of light that can be received by the photomultiplier tube 9 is 100 minutes of the amount of light of the commonly used forward scattering type. Is less than or equal to 1. Therefore, an argon ion laser is used as the gas laser 1 having a large output, and the size of the entire apparatus becomes large, resulting in a lack of maneuverability in measurement.

On the other hand, in order to solve such a problem, a small red semiconductor laser is used instead of the gas laser 1, and a small semiconductor light receiving element such as an avalanche photodiode is used instead of the photomultiplier tube 9. Conceivable.

However, the above red semiconductor laser is
The output is lower than that of the gas laser 1, and the amplification factor of the avalanche photodiode is 100 times that of the photomultiplier tube 9.
Since it is 1/0 or less, it cannot be operated as a backscattering type laser Doppler velocimeter at present.

Therefore, recently, as a means for solving such a problem, for example, in Japanese Patent Application No. 04-08422.
A semiconductor laser two-focus velocimeter described in No. 8 "has been proposed.

That is, this semiconductor laser two-focus velocimeter has a red semiconductor laser 11, a collimator lens 12 is provided on the optical axis of the red semiconductor laser 11, as shown in the schematic view of FIG. Is a parallel laser beam formed by reducing the divergence angle of the laser beam from the red semiconductor laser 11, and on the output side thereof, the laser beam is split into two laser beams with equal intensity and the polarization direction is changed. A Wollaston prism 13 as a prism is provided.

Further, on the output side of the Wollaston prism 13, the two split laser beams are supplied to the measurement area 4
Lens 1 which is a light collecting means for collecting two focal points on the
4 are provided.

FIG. 11 is an enlarged view showing the vicinity of the two focal points of the measurement area 4. As shown in FIG. 11, the diameter of the laser beam is expanded by the lens 14 after being narrowed down to the final diameter at the focus. By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 existing in the fluid to be measured 5 also pass through the measurement area 4, that is, two focal points at the same speed. When the fine particles 6 pass through the two focal points, the laser light is scattered, and the scattered light is collimated by the lens 14.

This parallel light is transmitted to the polarization filters 15a, 15
Only one of the scattered lights is selected by b, and the lens 16
The light is focused on the semiconductor light receiving elements 17a and 17b by a and 16b. Then, the semiconductor light receiving elements 17a, 17b
Signal output from the signal processing unit 1 as signal processing means
8, the time interval is measured, and the two focal lengths of the measurement area 4 are divided by the measured time interval to calculate the flow velocity. However, the velocity meter as described above cannot obtain information on the flow direction.

[0015]

As described above, in the conventional anemometer, the size of the entire device is large, the mobility of measurement is insufficient, the amount of reflected light is small, and accurate measurement cannot be performed. There was a problem that could not be obtained.

An object of the present invention is to provide a velocity meter capable of obtaining a large amount of reflected light, small in size, easy to move, easy and easy to perform an accurate measurement, and capable of obtaining a flow direction. is there.

[0017]

In order to achieve the above object, a velocity meter for measuring the velocity of fine particles in a fluid to be measured by using a laser beam and outputting the velocity as the fluid velocity to be measured is first described. In the invention according to claim 1, the semiconductor laser that generates the laser light, the collimator lens that reduces the divergence angle of the laser light from the semiconductor laser to form parallel laser light, and the laser light from the collimator lens Beam splitter for splitting into two laser beams having different widths, focusing means for focusing the split two laser beams from the beam splitter as two focal points having different widths, and measurement from the focusing means A semiconductor light receiving element provided so as to receive light from two focal points having different widths, and a flow direction and time based on an output signal from the semiconductor light receiving element. Interval was measured, the distance between the two foci and a signal processing means for the flow rate to the processing output of the vibration to the fluid to be measured in the measured time interval.

Further, in the invention according to claim 2, two semiconductor lasers for generating a laser beam and a collimator for forming two parallel laser beams having different widths by narrowing the divergence angle of the laser beam from the semiconductor laser. Condensing means for condensing the two laser beams from the lens and the collimator lens as two focal points with different widths in the measurement area, and light from the converging means from the focal points with two different widths in the measurement area. And a fluid to be measured by dividing the distance between two focal points by the measured time interval and measuring the flow direction and the time interval based on the output signal from the semiconductor light receiving element. And signal processing means for calculating and outputting the flow velocity of.

[0019]

[0020]

Furthermore, in the invention according to claim 3, wavelength
Two semiconductor lasers that generate different laser beams;
Reduce the divergence angle of the laser light from the semiconductor laser to reduce the width
Collimator lens that shapes parallel laser beams with different wavelengths
And two laser beams from the collimator lens
Focusing hand that focuses as two focal points with different widths in a fixed area
And the measurement area from the light collecting means through the interference filter.
2 arranged to receive light from one focal point of the area
Two semiconductor photo detectors and the output from each semiconductor photo detector
Measuring flow direction and time interval based on force signal,
Divide the two focal lengths by the measured time interval
Signal processing for calculating and outputting the flow velocity of the fluid to be measured
And means.

[0022]

Therefore, in the velocimeter of the present invention, the laser light from the semiconductor laser is focused as two focal points forming the measurement region, and thus the laser Doppler velocimeter forming the interference fringes in the measurement region is more effective. A large amount of reflected light can be obtained. As a result, the semiconductor light receiving element can obtain an electric signal having an S / N ratio sufficient for signal processing.

Information on the flow direction can be obtained by processing the output signal from the semiconductor light receiving element by making a difference between the two focal points. Furthermore, by using a semiconductor laser and a semiconductor light receiving element, it is possible to make a compact device, increase the mobility of the measurement, make the setting for the measurement easy, and perform accurate measurement easily and easily. Without
Long life and easy maintenance.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The anemometer of the present invention uses a semiconductor laser and a semiconductor light receiving element, is small in size and can be easily moved, and is a two-focus system in which two laser beams are focused as two focal points in a measurement region. By adopting, a large amount of reflected light can be obtained, the width of the two focal points can be changed,
By changing the bifocal wavelength using semiconductor lasers having different wavelengths, or changing the bifocal polarization state using a polarizing prism, a combination of these methods is used to make a difference between the bifocals, and Information on the flow direction is obtained by processing the output signal, the time interval of signal output from the semiconductor light receiving element is measured, and the two inter-focus distances are divided by the measured time interval, The flow velocity of the measurement fluid is calculated.

An embodiment of the present invention based on the above concept will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a schematic diagram showing a configuration example of a velocity meter according to a first embodiment of the present invention.

That is, as shown in FIG. 1, the velocimeter of this embodiment has a red semiconductor laser 21 for generating a laser beam.
A collimator lens 22 that forms a parallel laser beam by reducing the divergence angle of the laser beam from the red semiconductor laser 21, and a beam splitter 23 that splits the laser beam from the collimator lens 22 into two laser beams having different widths.
And a lens 24 which is a condensing means for condensing the two divided laser beams from the beam splitter 23 into the measurement region 4 as two focal points having different widths, and two widths of the measurement region 4 from the lens 24. Lenses 2 from different focal points
Semiconductor light receiving element 2 provided so as to receive light via 5
6 and the output signal from the semiconductor light receiving element 26, the flow direction and the time interval are measured, and the two focal lengths are divided (divided) by the measured time interval to obtain the fluid 5 to be measured. The signal processing unit 27 calculates and outputs the flow velocity of the existing fine particles 6.

Next, the operation of the anemometer of the present embodiment constructed as above will be described. In FIG. 1, the laser light from the red semiconductor laser 21 is shaped into a parallel laser light with its divergence angle reduced by a collimator lens 22 provided on the optical axis thereof. This collimator lens 2
The laser light from 2 is split into two laser lights having different widths with equal intensity by a beam splitter 23 provided on the output side. Then, the two split laser beams from the beam splitter 23 are focused on the measurement region 4 as two focal points having different widths by the lens 24 provided on the output side.

FIG. 2 is an enlarged view showing the vicinity of the two focal points of the measurement area 4. That is, as shown in FIG.
The diameter of the laser beam is narrowed down by the lens 24 to two different final diameters at the focal point, and then expanded. By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 existing in the fluid to be measured 5 also pass through the measurement area 4, that is, two focal points at the same speed. When the fine particles 6 pass through the two focal points, the laser light is scattered, and the scattered light is collimated by the lens 24. Further, this parallel light is condensed on the semiconductor light receiving element 26 by the lens 25.

The output signal from the semiconductor light receiving element 26 is input to the signal processing section 27 and converted into a square wave by the comparator. FIG. 3 is a waveform diagram showing an example of the result of conversion into this square wave. The width of the square wave in this Figure 3 is
It corresponds to the width of the two focal points in FIG. 2, from which the direction of flow can be seen.

Further, the signal processing unit 27 measures the time interval of signal output from the semiconductor light receiving element 26 and divides the two focal lengths by this time interval to calculate the flow velocity of the fluid 5 to be measured. .

As described above, in the anemometer of the present embodiment, the laser light from the red semiconductor laser 21 is focused on the two focal points forming the measurement area 4, so that the measurement area 4 is focused. It is possible to obtain a larger amount of reflected light than a laser Doppler velocimeter that forms interference fringes.
As a result, an electric signal having an S / N ratio sufficient for signal processing in the semiconductor light receiving element 26 can be obtained.

Further, the optical system from the red semiconductor laser 21 to the semiconductor light receiving element 26 is integrated.
That is, since the red semiconductor laser 21 is used as the light source and the scattered light from the two focal points is received by the semiconductor light receiving element 26, it is not necessary to adjust the optical axis at the time of measurement, and a small device can be obtained. The mobility of the measurement is increased, it is easy to carry to the measurement place and set for the measurement, and not only the accurate measurement can be performed easily and easily, but also the service life is long and the maintenance is easy.

As described above, the backscattering method can be used to measure the flow direction and the flow velocity, and at the same time, not only can a small device be easily and easily provided, but also have a long service life and easy maintenance.

(Second Embodiment) FIG. 4 is a schematic view showing a structural example of a velocity meter according to a second embodiment of the present invention.
The same elements as those in are denoted by the same reference numerals.

That is, in the velocity meter of this embodiment, as shown in FIG. 4, the two red semiconductor lasers 31a and 31b for generating laser light and the divergence angle of the laser light from the red semiconductor lasers 31a and 31b are made small. Collimator lenses 32a, 3 for forming two parallel laser beams having different widths
2b, a lens 24 which is a condensing means for condensing two laser beams from the collimator lenses 32a and 32b into the measurement area 4 as two focal points having different widths, and two widths of the measurement area 4 from the lens 24. Between the two focal points by measuring the flow direction and the time interval based on the output signal from the semiconductor light receiving element 26, which is provided so as to receive light from different focal points through the lens 25. The signal processing unit 27 divides the distance by the measured time interval (divides it) to calculate and output the flow velocity of the fine particles 6 existing in the fluid to be measured 5.

Next, the operation of the anemometer of the present embodiment constructed as above will be described. In FIG. 4, the laser beams from the two red semiconductor lasers 31a and 31b are shaped into two parallel laser beams having different widths by reducing the divergence angle by the collimator lenses 32a and 32b provided on the optical axes thereof. To be done. This collimator lens 32a,
The two laser beams from 32b are condensed in the measurement region 4 as two focal points having different widths by the lens 24 provided on the output side.

FIG. 2 is an enlarged view showing the vicinity of the two focal points of the measurement area 4. That is, as shown in FIG.
The diameter of the laser beam is narrowed down by the lens 24 to two different final diameters at the focal point, and then expanded. By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 existing in the fluid to be measured 5 also pass through the measurement area 4, that is, two focal points at the same speed. When the fine particles 6 pass through the two focal points, the laser light is scattered, and the scattered light is collimated by the lens 24. Further, this parallel light is condensed on the semiconductor light receiving element 26 by the lens 25.

The output signal from the semiconductor light receiving element 26 is input to the signal processing section 27 and converted into a square wave by the comparator. FIG. 3 is a waveform diagram showing an example of the result of conversion into this square wave. The width of the square wave in this Figure 3 is
It corresponds to the width of the two focal points in FIG. 2, from which the direction of flow can be seen.

Further, the signal processing unit 27 measures the time interval of signal output from the semiconductor light receiving element 26, divides the two focal lengths by this time interval, and calculates the flow velocity of the fluid 5 to be measured. .

As described above, in the anemometer of this embodiment, the laser beams from the two red semiconductor lasers 31a and 31b are focused on the two focal points forming the measurement area 4, It is possible to obtain a larger amount of reflected light than with a laser Doppler velocimeter that forms interference fringes in the measurement area 4. As a result, an electric signal having an S / N ratio sufficient for signal processing in the semiconductor light receiving element 26 can be obtained.

The two red semiconductor lasers 31a, 3a
The optical system from 1b to the semiconductor light receiving element 26 is integrated, that is, the red semiconductor lasers 31a and 31b are used as the light source, and the scattered light from the two focal points is received by the semiconductor light receiving element 26. , It is not necessary to adjust the optical axis during measurement, and it is possible to make it a compact device, which increases the mobility of measurement, makes it easy to carry it to the measurement location and make settings for measurement, making accurate measurement easy and easy. Not only can it be done, it will have a long life and be easy to maintain.

As described above, the backscattering method can be used to measure the flow direction and the flow velocity, and at the same time, the device can be easily and easily made into a small-sized device, and the life is long and the maintenance is easy.

(Third Embodiment) FIG. 5 is a schematic view showing a structural example of a velocity meter according to a third embodiment of the present invention.
The same elements as those in FIG. 4 are designated by the same reference numerals.

That is, as shown in FIG. 5, the velocity meter of the present embodiment has two red semiconductor lasers 51a and 51b for generating laser beams having different wavelengths and semiconductor lasers 51a and 51a.
Collimator lenses 52a and 52b for forming a parallel laser beam by reducing the spread angle of the laser beam from 51b,
The lens 24 which is a condensing means for condensing the two laser beams from the collimator lenses 52a and 52b into the measurement area 4 as two focal points, and one of the measurement area 4 from the lens 24 via the interference filters 55a and 55b. Two semiconductor light receiving elements 57a and 57b provided so as to receive light from one focus via lenses 56a and 56b, and a flow direction and a time interval based on output signals from the respective semiconductor light receiving elements 57a and 57b. Is measured, and the distance between the two focal points is divided (divided) by this measured time interval.
The signal processing unit 58 is configured to calculate and output the flow velocity of the fine particles 6 present therein.

Next, the operation of the anemometer of the present embodiment constructed as above will be described. In FIG. 5, the laser beams from the two red semiconductor lasers 51a and 51b are shaped into parallel laser beams with their divergence angles reduced by the collimator lenses 52a and 52b provided on the optical axes thereof. The two laser beams from the collimator lenses 52a and 52b are output by the lens 24 provided on the output side thereof.
The light is focused on the measurement area 4 as two focal points.

FIG. 6 is an enlarged view showing the vicinity of the two focal points of the measurement area 4. That is, as shown in FIG.
The diameter of the laser beam is narrowed down to the final diameter at the focus by the lens 24 and then expanded. By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 existing in the fluid to be measured 5 also pass through the measurement area 4, that is, two focal points at the same speed. When the fine particles 6 pass through the two focal points, the laser light is scattered, and the scattered light is reflected by the lens 24.
Is collimated by. Further, as for this parallel light, only one of scattered light is selected by the interference filters 55a and 55b, and the semiconductor light receiving element 5 is selected by the lenses 56a and 56b.
The light is focused on 7a and 57b.

The output signal from the semiconductor light receiving element 26 is input to the signal processing section 58, and in the signal processing section 58,
The direction of flow can be known from the time difference between the signal outputs from the semiconductor light receiving elements 57a and 57b.

Further, the signal processing unit 58 measures the time interval of signal output from the semiconductor light receiving elements 57a and 57b, divides the two focal lengths by this time interval, and calculates the flow velocity of the fluid to be measured 5. To be done.

As described above, in the anemometer of this embodiment, the laser beams from the two red semiconductor lasers 51a and 51b are focused on the two focal points forming the measurement area 4, It is possible to obtain a larger amount of reflected light than with a laser Doppler velocimeter that forms interference fringes in the measurement area 4. As a result, the semiconductor light receiving element 57a,
An electric signal having an S / N ratio sufficient for the signal processing of 57b can be obtained.

Two red semiconductor lasers 51a and 5a
The optical system from 1b to the semiconductor light receiving elements 57a and 57b is integrated, that is, the red semiconductor lasers 51a and 51b are used as the light source so that the scattered light from two focal points is received by the semiconductor light receiving elements 57a and 57b. Therefore, it is not necessary to adjust the optical axis during measurement,
It is possible to make it a small device and increase the mobility of the measurement, and it becomes easy to carry it to the measurement place and set it for the measurement,
Not only is accurate measurement simple and easy, but it also has a long service life and easy maintenance.

As described above, the backscattering method can be used to measure the flow direction and the flow velocity, and at the same time, not only can a small device be easily and easily provided, but it can also have a long life and be easily maintained.

(Fourth Embodiment) FIG. 7 is a schematic diagram showing a structural example of a velocity meter according to a fourth embodiment of the present invention. The same elements as those in FIGS. 1, 4 and 5 are the same. It is shown with reference numerals.

That is, as shown in FIG. 7, the velocity meter of the present embodiment has a red semiconductor laser 71 for generating laser light.
And a collimator lens 72 for forming a parallel laser beam by reducing the divergence angle of the laser beam from the red semiconductor laser 71, and dividing the laser beam from the collimator lens 72 into two laser beams and changing the polarization direction. A Wollaston prism 73, which is a polarizing prism, a lens 24, which is a condensing unit that condenses the two laser beams from the Wollaston prism 73 into two focal points on the measurement region 4, and polarization filters 75a and 75b. Light from one focal point of the measurement region 4 from the lens 24 is reflected by the lenses 76a and 76b.
Two semiconductor light receiving elements 77a, 77b provided so as to receive light via
The flow direction and the time interval are measured on the basis of the output signal from and the two inter-focus distances are divided (divided) by the measured time interval to obtain the flow velocity of the fine particles 6 existing in the fluid to be measured 5. It is composed of a signal processing unit 78 that performs arithmetic processing and outputs.

Next, the operation of the anemometer of the present embodiment constructed as above will be described. In FIG. 7, the laser light from the red semiconductor laser 71 is shaped into parallel laser light with its divergence angle reduced by a collimator lens 72 provided on its optical axis. This collimator lens 7
The Wollaston prism 73 provided on the output side splits the laser beam from 2 into two laser beams of equal intensity, changes the polarization direction, and focuses the laser beam on the measurement region 4 as two focal points.

FIG. 6 is an enlarged view showing the vicinity of the two focal points of the measurement area 4. That is, as shown in FIG.
The diameter of the laser beam is narrowed down to the final diameter at the focus by the lens 24 and then expanded. By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 existing in the fluid to be measured 5 also pass through the measurement area 4, that is, two focal points at the same speed. When the fine particles 6 pass through the two focal points, the laser light is scattered, and the scattered light is reflected by the lens 24.
Is collimated by. Further, as for this parallel light, only one of scattered light is selected by the polarization filters 75a and 75b, and the semiconductor light receiving element 7 is selected by the lenses 76a and 76b.
It is focused on 7a and 77b.

The output signals from the semiconductor light receiving elements 77a and 77b are input to the signal processing section 78, and the signal processing section 7 receives the signals.
8, the direction of the flow can be known from the time difference between the signal outputs from the semiconductor light receiving elements 77a and 77b.

Further, the signal processing unit 78 measures the time interval of signal output from the semiconductor light receiving elements 77a and 77b, divides the two focal lengths by this time interval, and calculates the flow velocity of the fluid to be measured 5. To be done.

As described above, in the anemometer of the present embodiment, the laser light from the red semiconductor laser 71 is focused on the two focal points forming the measurement area 4, so that the measurement area 4 is focused. It is possible to obtain a larger amount of reflected light than a laser Doppler velocimeter that forms interference fringes.
As a result, an electric signal having an S / N ratio sufficient for signal processing of the semiconductor light receiving elements 77a and 77b can be obtained.

Further, the optical system from the red semiconductor laser 71 to the semiconductor light receiving elements 77a and 77b is integrated, that is, the red semiconductor laser 71 is used as a light source, and scattered light from two focal points is received by the semiconductor light receiving element 77.
Since the light is received by a and 77b, there is no need to adjust the optical axis during measurement, the device can be made compact and the mobility of measurement is increased, and it is possible to carry it to the measurement location and make settings for measurement. Not only is it easier and more accurate to make accurate measurements, but it also has a longer life and easier maintenance.

As described above, the direction of the flow and the flow velocity can be measured by the backscattering method, and at the same time, not only a small device can be easily and easily provided, but also a long life and easy maintenance are possible.

(Fifth Embodiment) FIG. 8 is a schematic view showing a structural example of a velocity meter according to a fifth embodiment of the present invention, which is the same element as that of FIGS. 1, 4, 5, and 7. Are denoted by the same reference numerals.

That is, as shown in FIG. 8, the anemometer of the present embodiment has two red semiconductor lasers 81a and 81b for generating laser beams having different wavelengths and a red semiconductor laser 81.
Collimator lens 82 for forming parallel laser beams having different widths by reducing the divergence angle of the laser beams from a and 81b
a, 82b, a lens 24 which is a condensing means for condensing the two laser beams from the collimator lenses 82a, 82b as two focal points having different widths in the measurement region 4, and the lenses via the interference filters 55a, 55b. Two semiconductor light receiving elements 5 provided so as to receive the light from one focal point of the measurement area 4 from 24 via the lenses 56a and 56b.
7a and 57b and the output signals from the respective semiconductor light receiving elements 57a and 57b, the flow direction and the time interval are measured, and the two focal lengths are divided (divided) by the measured time interval. The signal processing unit 88 is configured to calculate and output the flow velocity of the fine particles 6 existing in the measurement fluid 5.

Next, the operation of the anemometer of the present embodiment constructed as above will be described. In FIG. 8, the laser lights from the two red semiconductor lasers 81a and 81b are collimated by the collimator lenses 82a and 82b provided on the optical axes thereof so that the divergence angles of the laser lights are reduced and parallel laser lights having different widths are obtained. Molded. This collimator lens 82
The two laser beams from a and 82b are focused on the measurement region 4 as two focal points having different widths by the lens 24 provided on the output side.

FIG. 2 is an enlarged view showing the vicinity of the two focal points of the measurement area 4. That is, as shown in FIG.
The diameter of the laser beam is narrowed down by the lens 24 to two different final diameters at the focal point, and then expanded. By flowing the fluid to be measured 5 into the measurement area 4, the fine particles 6 existing in the fluid to be measured 5 also pass through the measurement area 4, that is, two focal points at the same speed. When the fine particles 6 pass through the two focal points, the laser light is scattered, and the scattered light is collimated by the lens 24. Further, only one of the scattered lights of the parallel light is selected by the interference filters 55a and 55b, and is focused on the semiconductor light receiving elements 57a and 57b by the lenses 56a and 56b.

The output signals from the semiconductor light receiving elements 57a and 57b are input to the signal processing unit 88, converted into a square wave by the comparator, and the measurement accuracy in the flow direction is improved by measuring the width and the time difference.

Further, the signal processing unit 88 measures the time interval of signal output from the semiconductor light receiving elements 57a and 57b, divides the two focal lengths by this time interval, and calculates the flow velocity of the fluid to be measured 5. To be done.

As described above, in the anemometer of this embodiment, the laser light from the two red semiconductor lasers 81a and 81b is focused on the two focal points forming the measurement area 4, It is possible to obtain a larger amount of reflected light than with a laser Doppler velocimeter that forms interference fringes in the measurement area 4. As a result, the semiconductor light receiving element 57a,
An electric signal having an S / N ratio sufficient for the signal processing of 57b can be obtained.

The two red semiconductor lasers 81a and 81a
The optical system from 1b to the semiconductor light receiving elements 57a and 57b is integrated, that is, two red semiconductor lasers 81a and 81b are used as light sources, and the scattered light from two focal points is received by the semiconductor light receiving elements 57a and 57b. Since it does not require adjustment of the optical axis at the time of measurement, it can be made a small device, the mobility of measurement increases, and it becomes easy to carry it to the measurement place and set it for measurement. Not only is the measurement easy and easy, but it also has a long life and is easy to maintain.

As described above, it is possible to measure the flow direction and the flow velocity by the backscattering method, and at the same time, not only can a small device be easily and easily provided, but also have a long service life and easy maintenance.

In each of the above embodiments, the case where the red semiconductor laser is used as the semiconductor laser has been described, but the present invention is not limited to this, and the present invention is also applicable to the case where a semiconductor laser of a color other than red is used as the semiconductor laser. Is similarly applied, and the same effect as described above can be obtained.

[0071]

As described above, according to the present invention, many
Accurate measurement with a small amount of reflected light, easy to move and compact
Is easy and easy, and can get the flow direction
A possible anemometer can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a velocity meter according to the present invention.

FIG. 2 is an enlarged view showing a measurement area in the first embodiment.

FIG. 3 is a diagram showing an example of signal output from a comparator in the signal processing unit in the first embodiment.

FIG. 4 is a schematic configuration diagram showing a second embodiment of the velocity meter according to the present invention.

FIG. 5 is a schematic configuration diagram showing a third embodiment of the velocity meter according to the present invention.

FIG. 6 is an enlarged view showing a measurement region in the third embodiment.

FIG. 7 is a schematic configuration diagram showing a fourth embodiment of the velocity meter according to the present invention.

FIG. 8 is a schematic configuration diagram showing a fifth embodiment of the velocity meter according to the present invention.

FIG. 9 is a schematic diagram showing a configuration example of a conventional velocity meter.

FIG. 10 is a schematic diagram showing a configuration example of a conventional semiconductor laser two-focus velocimeter.

FIG. 11 is an enlarged view showing a measurement region in the semiconductor laser two-focus velocimeter.

[Explanation of symbols]

4 ... Measuring area, 5 ... Fluid to be measured, 6 ... Fine particles, 21, 3
1a, 31b, 51a, 51b, 71, 81a, 81b
... Red semiconductor lasers, 22, 32a, 32b, 52a,
52b, 72, 82a, 82b ... Collimator lens, 2
3, 73 ... Beam splitter, 24 ... Lens, 25, 5
6a, 56b, 76a, 76b ... Lens, 55a, 55
b ... interference filter, 75a, 75b ... polarization filter, 2
6, 57a, 57b, 77a, 77b ... Semiconductor light receiving element, 24, 58, 78, 88 ... Signal processing section.

Claims (3)

(57) [Claims] 1. A velocity meter for measuring the velocity of fine particles in a fluid to be measured using laser light and outputting the velocity as the fluid velocity to be measured. A collimator lens that forms a parallel laser beam by reducing the divergence angle of the laser beam, a beam splitter that splits the laser beam from the collimator lens into two laser beams having different widths, and a beam splitter that splits the beam from the beam splitter. Condensing means for condensing the two laser beams into the measurement area as two focal points having different widths, and light converging means for receiving light from the focal points having two different widths in the measuring area. A semiconductor light receiving element and a flow direction and a time interval are measured based on an output signal from the semiconductor light receiving element, and the two focal lengths are measured. And a signal processing means for calculating and outputting the flow velocity of the fluid to be measured divided by a time interval. 2. A velocity meter for measuring the velocity of fine particles in a fluid to be measured using laser light and outputting the velocity as the fluid velocity to be measured, two semiconductor lasers generating laser light, and the semiconductor laser. Collimator lens for forming two parallel laser beams having different widths by reducing the divergence angle of the laser beam from the laser beam, and condensing the two laser beams from the collimator lens as two focal points having different widths in the measurement area. And a semiconductor light receiving element provided so as to receive light from two focal points having different widths in the measurement region from the light collecting means, and a flow of light based on an output signal from the semiconductor light receiving element. Signal processing means for measuring a direction and a time interval, dividing the two focal lengths by the measured time interval, and processing and outputting the flow velocity of the fluid to be measured. An anemometer characterized by comprising: 3. Fine particles in a fluid to be measured using laser light
Of the measured fluid velocity is output as the measured fluid velocity.
At a flow rate meter for two semiconductor lasers for generating laser beams having different wavelengths
And reduce the divergence angle of the laser light from the semiconductor laser.
Collimator lens for forming parallel laser beams with different widths
And the two laser beams from the collimator lens
Condensing means for converging two focal points with different widths in the area
And one of the measurement areas from the condensing means via the interference filter.
Two halves arranged to receive light from one focal point
Based on the output signals from the conductor light receiving element and the semiconductor light receiving elements,
The direction and the time interval are measured, and the distance between the two focal points is calculated.
Flow velocity of the fluid to be measured divided by the measured time interval
And a signal processing means for processing and outputting the signal .