JPH0815437A - Laser-velocity measuring device - Google Patents

Abstract

PURPOSE:To discriminate the direction of movement of fine particles by comparatively simple constitution in a laser-velocity measuring device, in which two laser beams are crossed and particle velocity is detected from the scattered light of the fine particles passing through a cross region. CONSTITUTION:The laser beams of a semiconductor laser 1 are divided by a beam splitter 2, and focussed at one point by a condenser lens 3, Scattered light passing through an interference fringe formed in a cross region 4 is focussed by a condenser lens 5, and received by a photodiode 6. A two-piece type photodiode is used as the photodiode 6. When an output is obtained from both two regions of the photodiode 6, the direction is discriminated on the basis of the order of light reception.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser velocity measuring device for measuring the velocity of fine particles.

[0002]

2. Description of the Related Art Conventionally, a device for measuring a particle velocity using a laser beam has been proposed by paying attention to the characteristics of a laser beam excellent in coherence and monochromaticity. ing. A dual-beam laser velocimeter intersects laser beams having the same plane of polarization at one point to form interference fringes, and the scattered light generated when particles pass through the intersecting region causes a periodic intensity change corresponding to the interference fringes. Since it has, the particle velocity is measured. The conventional laser velocity measuring device that forms such interference fringes cannot detect the moving direction of the particles. Therefore, as disclosed in, for example, Japanese Patent Laid-Open No. 62-43569, there is known a device in which a Bragg cell is used to shift the frequency of either one of the dual beam laser beams to form an interference fringe. When the interference fringes are formed using such a Bragg cell, the interference fringes move at a speed corresponding to the speed of frequency shifting in a predetermined direction, so that the moving direction is changed based on the obtained frequency analysis result. Can be determined.

[0003]

However, in such a conventional laser velocity measuring apparatus, an expensive Bragg cell is required, and it is necessary to determine the direction after receiving the signal and analyzing the frequency. However, there is a drawback that the configuration of is complicated.

The inventions according to claims 1 to 3 of the present application have been made in view of such conventional problems, and a laser velocity measuring device capable of determining the moving direction of particles with a relatively simple structure. The purpose is to provide.

In addition to this problem, an object of the invention of claim 4 of the present application is to make it possible to determine the moving direction of particles in two dimensions.

[0006]

According to a first aspect of the present invention, a laser light source for generating a laser light of a single wavelength and a laser light obtained from the laser light source are divided into two beams to form a pair of light beams. Separation means, first optical means for intersecting a pair of light beams provided by the beam separation means at one point, and second optical means for condensing scattered light obtained when particles pass through the intersection area. A first photoelectric conversion for dividing the light receiving region into two first and second light receiving regions by one dividing line, receiving the scattered light condensed by the second optical means, and converting the scattered light into an electric signal. And the first of the first photoelectric converters
Of the first and second light receiving areas of the first photoelectric converter while the output is being obtained from the adding means. When a light reception signal is obtained, a direction determination means for determining the moving direction of particles according to the light reception order, and a velocity detection means for detecting the velocity of particles passing through the intersection region from the AC component of the output of the first photoelectric converter. And are provided.

According to a second aspect of the present invention, there is provided a laser light source for generating a laser beam having a single wavelength, a beam splitting means for splitting the laser beam obtained from the laser light source into two light beams, and a beam splitting device. The first optical means for intersecting the pair of light beams provided by the means at one point, the second optical means for condensing scattered light obtained when the particles pass through the intersection area, and the light receiving area A first photoelectric converter for receiving the scattered light, which is divided into first and second light receiving regions by the two dividing lines and condensed by the second optical means, and converting it into an electric signal; A second photoelectric converter that receives scattered light collected by the optical means and converts the scattered light into an electric signal, and while the output is being obtained from the second photoelectric converter, the first photoelectric converter When the light receiving signal is continuously obtained from the second light receiving area, the light receiving sequence Therefore, it is provided with a direction determining means for determining the moving direction of the particles, and a speed detecting means for detecting the speed of the particles passing through the intersection region from the AC component of the output of the second photoelectric converter. Is.

According to the invention of claim 4 of the present application,
A laser light source that generates a laser beam of a second wavelength;
The laser light obtained from the laser light source of the second wavelength is 2
A first beam beam splitting means that splits the beam beam into two pairs of light beams including two pairs of laser beams and having two perpendicular surfaces, and two pairs of light beams provided by the beam beam splitting means intersect at one point.
And second optical means for collecting scattered light obtained when the particles pass through the intersecting region, and two perpendicular to each other.
The light-receiving region is divided into four by the line of the first to fourth light-receiving regions, and the first and second light-receiving regions and the first and third light-receiving regions are divided so as to be adjacent to each other, A first photoelectric converter that receives scattered light of the first and second wavelengths collected by the second optical means and converts the scattered light into an electric signal, and a first photoelectric converter collected by the second optical means. A second photoelectric converter for receiving scattered light of a wavelength and converting it into an electric signal, and a third photoelectric conversion for receiving scattered light of the second wavelength condensed by the second optical means and converting it into an electric signal. And a first adding means for adding outputs of the first and second light receiving regions of the first photoelectric converter which are adjacent to each other, and the third and fourth of the first photoelectric converter which are adjacent to each other.
Second adding means for adding the outputs of the light receiving areas of the first and third adding means for adding the outputs of the first and third light receiving areas of the first photoelectric converter which are adjacent to each other, and the first photoelectric conversion. Of the second and fourth light receiving regions adjacent to each other of the converter, and while the output is obtained from the third photoelectric converter, When signals are continuously obtained, the direction is discriminated based on the order of the outputs Y
While the output is being obtained from the direction determining means and the second photoelectric converter, when the signals are continuously obtained from the third and fourth adding means, the direction is determined based on the order of the outputs. X
Direction determining means, Y direction speed detecting means for detecting the speed in the Y direction from the frequency based on the output of the third photoelectric converter, and X direction from the frequency based on the output of the second photoelectric converter. And an X-direction speed detecting means for detecting a speed.

[0009]

According to the invention of claim 1 of the present application having such characteristics, the laser light of the laser light source is separated by the beam separating means, and the first optical means intersects at one point. In this way, interference fringes are formed in the intersection area. If the fine particles pass through the intersection area, scattered light is obtained, and the scattered light is collected by the second optical means and received by the first photoelectric converter. Since the first photoelectric converter is divided into the first and second light receiving regions, the moving direction of the particle is discriminated by the direction discriminating means according to the light receiving order while the added output of these is obtained. I am trying. Further, the velocity of particles can be detected from the AC component of the adding means based on the frequency thereof.

According to the second aspect of the present invention, instead of the adding means, a second photoelectric converter for receiving scattered light from all regions of the intersection region is used. Therefore, the velocity of the particles can be detected without using the adding means.

Further, according to the invention of claim 4, laser light sources having different wavelengths are provided, and each of them is divided into two pairs of light beams, and the light beams are separated into two pairs.
Focus at a point. Thus, when the particles pass through the intersection area, the scattered light is collected by the second optical means,
The light is received by the four-division type first photoelectric converter having the fourth light receiving region and the second and third photoelectric converters having sensitivity to the light of the first and second wavelengths, respectively. Then, the outputs of the four-division type photoelectric converters are added by the first to fourth adding means for each of the light receiving regions adjacent to each other. When the output of the second or third photoelectric converter is obtained in this way, based on the output order of the first and second adding means and the output order of the third and fourth adding means, the Y direction And the sign of the direction of the particles in the X direction is determined. At the same time, the velocity components in the Y direction and the X direction are calculated from the AC components of the outputs of the second and third photoelectric conversions.

[0012]

1 is a schematic diagram showing the construction of an optical system of a laser velocity measuring apparatus according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing the construction of its signal processing unit. In these figures, a laser light source of a single wavelength, for example, a laser beam of a semiconductor laser 1 is given to a beam splitter 2. The beam splitter 2 is a separating means for separating a given laser beam into two parallel laser beams having the same light intensity,
The laser beam is incident on the focusing lens 3. The focusing lens 3 is a first optical means for focusing the parallel laser beam on the intersection area 4 of one point. Light scattered by particles passing through the intersection area 4 is condensed by the lens 3, and further scattered light is condensed by the lens 5 at one point. The lenses 3 and 5 form second optical means for collecting scattered light. At the focal position of the lens 5, a first photoelectric converter having first and second light receiving regions, for example, a two-divided photodiode 6 is arranged. As shown in the enlarged view from the side of the condenser lens 5 in FIG. 1A, the two-divided photodiode 6 has a half thereof as a light receiving region PD1 and an upper half thereof as a light receiving region PD2.
It is preferable that the light receiving region is divided in a direction parallel to the direction of the interference fringes formed in the intersecting region as shown in FIG. 1B, that is, in the horizontal direction in the illustrated case. A pair of outputs from these light receiving regions are given to the signal processing unit 7.

In FIG. 2, the signal processing section 7 has amplifiers 10 and 11 for converting the outputs of the light receiving regions PD1 and PD2 of the photodiode 6 into voltages and amplifying them, respectively, and these outputs are output from the direction discriminating means 12. It is given to the AM detectors 13 and 14 and the adder 15. The adder 15 is the amplifier 1
It is addition means for adding the outputs of 0 and 11, and its output is input to the AM detector 16 and the AC amplifier 17. A
The M detectors 13, 14 and 16 are detectors that perform envelope detection of the input signal, and their outputs are input to the comparators 18 to 20, respectively. The comparators 18 to 20 discriminate the input signal by a predetermined threshold value and binarize it, and the output thereof is inputted to the direction discriminating circuit 21. The direction discriminating circuit 21 discriminates the direction only when signals are obtained from both the comparators 18 and 19 while an output is being obtained from the comparator 20. This direction determination is determined as either the + direction or the-direction depending on whether the signal is first input to either of the comparators 18 and 19. The discrimination output is output to the outside and also to the frequency analysis circuit 22 at the same time. On the other hand, AC amplifier 17
The AC component of the output of the adder 15 is amplified and output to the frequency analysis circuit 22. Frequency analysis circuit 22
Is a speed detecting means for calculating the speed based on the frequency of the output of the AC amplifier 17 when the direction discrimination output is obtained. The frequency analysis circuit 22 is, for example, a fast Fourier transform (F
FT) is performed and a signal having a frequency exceeding a predetermined level on the frequency axis is output as the particle velocity.

Next, the operation of this embodiment will be described with reference to the time chart of FIG. First, when the semiconductor laser 1 is oscillated in FIG. 1, the laser beam is separated by the beam splitter 2 and becomes a parallel laser beam, which is focused by the lens 3 at one point. At this time, interference fringes are formed in the intersection area 4 as shown in an enlarged view in FIG.

Now, let it be assumed that fine particles have passed through the intersecting region in the positive direction of the X axis. When the fine particles pass in the positive direction of the X axis, they penetrate the intersection region 4 and a signal having an amplitude corresponding to the interference fringes is obtained by the photodiode 6 which is a photoelectric converter. At this time, when passing in the + direction of the X axis,
First, a signal is obtained on the light receiving region PD1 side, and then is incident on the light receiving region PD2 side. Therefore, as shown in FIGS. 3A and 3B, the signals obtained in the light receiving regions PD1 and PD2 have a slight time lag. Meanwhile adder 15
3 (c) because the output of is the sum of these.
As shown in, the signal includes these. Therefore, the outputs of the AM detectors 13, 14 and 16 are as shown in FIGS.
It becomes an envelope signal of the signal shown in (c), which is binarized by the comparators 18 to 20 to obtain an envelope signal shown in FIG.
The signals (f) to (f) are obtained. Time like this
If the particles P move the intersection region 4 in the + direction of the X axis between t _{1 and} t ₃ , first the output of the comparator 20 is obtained from the side of the comparator 18 while the output of the comparator 20 is at the H level, and then the output of the comparator 19 is output. Is obtained. The direction discriminating circuit 21 discriminates that the fine particles have passed in the + direction of the X-axis according to the input order in this way. Such a determination result is output to the outside and is also input to the frequency analysis circuit 22 at the same time. The frequency analysis circuit 22 calculates and outputs the particles of the object by the frequency only from the high frequency component of the adder 15 only when the direction determination signal is obtained. In this way, the direction and speed of the object can be determined at the same time without error.

[0016] Now particles P 'is X-axis - when passing through the intersection region 4 in a direction, first signal is obtained in the light receiving region PD2 side as shown at time t ₄ ~t _6, then the light receiving regions PD1
Signal is obtained. Therefore, by performing the same processing, while the output from the comparator 20 is being obtained, the output is first obtained from the comparator 19 and then from the comparator 18, and it can be determined that the fine particles have passed in the negative direction. it can. In this case as well, the velocity component of the particle in the X-axis direction can be similarly determined based on the frequency.

Now, the fine particles are in one of the intersection regions 4, for example, P
When only the area where scattered light is obtained in D1
A signal is obtained only from the light receiving region PD1 side, and the light receiving region PD2
Can't get any output. In this case, since the direction cannot be discriminated, the direction discriminating circuit 21 does not output the direction discriminating output and gives a prohibition signal to the frequency analyzing circuit 22. In this case, speed calculation is prohibited to prevent erroneous output. Further, even when a plurality of particles successively pass through, the outputs of the comparators 18 and 19 may be erroneously determined before and after. Therefore, such an error can be prevented in advance by discriminating these contexts only while the comparator 20 is at the H level.

Although the photodiode 6 is arranged at the focal position of the condenser lens 5 in the above-described first embodiment, the half mirror 8 is provided between the condenser lens 5 and the photodiode 6 as shown in FIG. The photodiode 6 may be provided at a position where the half mirror 8 is transmitted and the photodiode 9 may be provided at a position where the half mirror 8 is reflected. The photodiode 9 is a second photoelectric converter that converts scattered light obtained from all portions of the laser beam intersection region into an electric signal, and its output is given to the signal processing unit 7A. The signal processing unit 7A is shown in FIG.
Although it is almost the same as the above, the amplified output of the photodiode 9 instead of the adder 15 is directly output to the AM of the direction discriminating means 12.
It is given to the detector 16 and the AC amplifier 17 for processing. In this case, since the addition process is not necessary, the speed can be detected with higher sensitivity.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a perspective view showing an optical system portion of the second embodiment. In this figure, a semiconductor laser 31
Is a laser light source that oscillates a laser beam having a second wavelength λ2, which is different from the wavelength λ1, and the semiconductor laser 32. The beam splitters 33 and 34 are beam separating means for separating the incident laser beam into parallel planes along the X axis and the Y axis, and the center lines of the separated laser beams are made common. Then, these four laser beams are focused at one point by the focusing lens 35. Then, in the intersection area 36, the laser beam in the plane including the X axis separated by the beam splitter 33 is used as in the first embodiment, as shown in FIG.
The interference fringes shown in (b) are formed. Further, the laser beam output from the beam splitter 34 forms vertical interference fringes shown in FIG. 5C in the same intersection region 36. When passing through the intersection area 36, scattered light is obtained. This scattered light is condensed by the focusing lens 35,
It is reflected by the mirror 37. And half mirror 3
The scattered light is separated by 8 and one is condensed by a condenser lens 39.
Through the photodiode 40, which is the first photoelectric converter.
Lead to. The light transmitted through the half mirror 38 is further incident on the half mirror 41. The light reflected by the half mirror 41 and the transmitted light are guided to the photodiodes 42 and 43 which are the second and third photoelectric converters through the condenser lenses, respectively. Here, as shown in FIG. 5D, the photodiode 40 has an X axis and a Y axis as viewed from the Z axis direction, that is, FIG.
The light receiving region is divided into four first to fourth regions by two lines parallel to the interference fringes of the intersecting regions shown in (b) and (c), and the respective light receiving regions are designated as PD1 to PD4. Here, the first and second light receiving regions PD1 and PD2 and the first and third light receiving regions PD1 and PD
3 are adjacent to each other, and the light receiving regions PD1 and PD3 are assumed to be symmetrical to each other. On the other hand, the photodiodes 42 and 43 have color filters 44 and 45 on their front surfaces.
Are arranged at substantially the same position and detect scattered light in all parts of the intersection area. The color filters 44 and 45 separate scattered light for each wavelength λ1 and λ2. The photodiode 42 receives the laser light of the first wavelength λ1, and the photodiode 43 receives the laser light of the second wavelength λ2.

Next, the configuration of the signal processing unit 50 using the three photodiodes 40, 42 and 43 of the third embodiment will be described with reference to FIG. The outputs of the light receiving regions PD1 to PD4 of the photodiode 40 are input to the first to fourth adders 51 to 54 and added. The first adder 51 adds the outputs of the light receiving regions PD1 and PD2, and the second adder 5
Reference numeral 2 denotes an addition means for adding the outputs of the light receiving areas PD3 and PD4, the third adder 53 adds the outputs of the light receiving areas PD1 and PD3, and the fourth adder 54 the light receiving areas PD2 and PD.
It is an adding means for adding the outputs of 4 and 4, respectively. Adder 5
The outputs of 1, 52 are input to the Y-direction direction determining means 12Y, respectively. Photodiode 4 which is the third photoelectric converter
The output of No. 3 is given to the direction discriminating means 12Y and the AC amplifier 17Y via the amplifier 55. The internal block of the direction discriminating means 12Y is the direction discriminating means 12 of the first embodiment described above.
Similar to the above, the direction is discriminated from the order by AM detection and binarization. The AC amplifier 17Y is the first
This corresponds to the AC amplifier 17 of the embodiment, and its high frequency component is input to the frequency analysis circuit 22Y. The frequency analysis circuit 22Y analyzes and outputs the velocity component in the Y direction based on the frequency of the input signal only when the determination signal is obtained from the direction determination means 12Y.

On the other hand, the outputs of the adding means 53 and 54 are input to the direction discriminating means 12X in the X direction. The output of the photodiode 42 is input to the direction determining means 12X and the AC amplifier 17X via the amplifier 56. Direction determination means 12X
Also has the same configuration as the direction discriminating means 12 of the first embodiment, and discriminates positive or negative in the X direction based on these inputs. This direction determination output is output to the outside and is also input to the frequency analysis circuit 22X at the same time. The frequency analysis circuit 22X detects the velocity component in the X-axis direction based on the frequency of the output of the AC amplifier 17X only when the direction determination signal is obtained from the direction determination means 12X.

Next, the operation of this embodiment will be described. As shown in FIG. 7A, the fine particles P passing through the intersection region 36.
When a passes in the Y direction and passes through the light receiving regions PD3 and PD1 as seen from the photodiode side, the adders 52 and 5 are added.
Outputs are sequentially obtained from 1. Therefore, the direction determination output and the speed signal can be output from the Y direction determination block as in the first embodiment. In this case, since the light does not pass through the light receiving regions PD2 and PD4 of the photodiode, no output can be obtained from the adder 54. Therefore, no direction signal is obtained in the X direction, and the speed is not calculated.
Similarly, when the fine particles Pb pass in the direction from the light receiving region PD4 to PD1 as shown in FIG. 7A, signals are obtained in the adders 52 and 51, and the negative direction in the Y direction and An output is obtained from the frequency analysis circuit 22Y.
In this case, an output is obtained from the adder 54, but no output is obtained from the adder 53, so that the direction signal in the X direction and the velocity signal are not output.

Similarly, as shown in FIG. 7B, when the fine particles Pc pass through the light receiving regions PD1 and PD2, or when the fine particles Pd pass from the light receiving regions PD4 to PD3, the direction is from the X direction only. A signal and a speed signal will be obtained. Further, as shown in FIG. 7C, the light receiving area PD4
When passing from PD to PD2 and moving to the position of PD1, the direction signal and the speed signal are obtained from both the X direction and the Y direction.

In each of the above-mentioned embodiments, the scattered light of the fine particles passing through the intersection area is received backward and the direction and velocity signals are output. However, the direction and velocity are scattered based on the scattered light forward. Needless to say, can be detected.

Further, in the third embodiment, two semiconductor lasers 31 and 32 which generate laser beams having different wavelengths are used as the laser light source, but a laser light source which emits two colors such as Ar laser may be used. Needless to say.

[0026]

As described above in detail, according to the inventions of claims 1 to 4 of the present application, the passage direction and velocity component of the fine particles passing through the intersection region portion can be determined without using a Bragg cell with a relatively simple structure. The effect that it can be detected is obtained. In addition to the above, the invention of claim 4 has the effect of being able to detect the positive and negative velocity components in the two directions of the X-axis and the Y-axis and the respective velocity components.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical system of a laser velocity measuring device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a signal processing unit of the laser velocity measuring apparatus according to the first embodiment of the present invention.

FIG. 3 is a time chart showing an operating state of the laser velocity measuring device according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of an optical system of a laser velocity measuring device according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of an optical system of a laser velocity measuring device according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a signal processing unit of a laser velocity measuring device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing various examples of passing directions through a light receiving sensor of a laser velocity measuring device according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 31, 32 Semiconductor laser 2, 33, 34 Beam splitter 3, 35 Focusing lens 4, 36 Crossing area 5, 39, 41 Condensing lens 6, 40, 42, 43 Photodiode 12, 12X, 12Y Direction discriminating means 13 , 14, 16 AM detector 15, 51, 52, 53, 54 Adder 17, 17X, 17Y AC amplifier 18, 19, 20 Comparator 22, 22X, 22Y Frequency analysis circuit 21 Direction determination circuit 37 Mirror 38 Half mirror

Claims (4)

[Claims] 1. A laser light source for generating a laser beam of a single wavelength, a beam splitting means for splitting the laser light obtained by the laser light source into two light beams, and a pair provided by the beam splitting means. 1 light beam
First optical means for intersecting at a point, second optical means for collecting scattered light obtained when particles pass through the intersecting area, and a light receiving area for the first and first A first photoelectric converter that divides the light into two light-receiving regions and receives scattered light that is collected by the second optical means and converts the scattered light into an electric signal; and a first photoelectric converter of the first photoelectric converter. Addition means for adding received light signals obtained from the light receiving area and the second light receiving area, and continuation from the first and second light receiving areas of the first photoelectric converter while the output is obtained from the adding means. Direction determining means for determining the moving direction of particles according to the light receiving sequence when a light receiving signal is obtained, and a speed for detecting the speed of particles passing through the intersection region from the AC component of the output of the first photoelectric converter. A laser speed, characterized by comprising: Measuring device. 2. A laser light source for generating a laser light of a single wavelength, a beam separating means for dividing the laser light obtained by the laser light source into two light beams, and a pair provided by the beam separating means. 1 light beam
First optical means for intersecting at a point, second optical means for collecting scattered light obtained when particles pass through the intersecting area, and a light receiving area for the first and first A first photoelectric converter, which is divided into two light receiving regions and receives scattered light condensed by the second optical means and converts it into an electric signal, and is condensed by the second optical means. A second photoelectric converter for receiving scattered light and converting it into an electric signal; and first and second light receiving regions of the first photoelectric converter while an output is being obtained from the second photoelectric converter. Further, when the light reception signal is continuously obtained, the direction determination means for determining the moving direction of the particle according to the light reception order, and the velocity of the particle passing through the intersection region from the AC component of the output of the second photoelectric converter are detected. And a laser velocity measuring means for Apparatus. 3. The laser according to claim 1, wherein the first photoelectric converter is arranged such that a light receiving area thereof is separated in parallel with an interference fringe of an intersecting area. Speed measuring device. 4. A laser light source for generating laser light of different first and second wavelengths, and a laser light obtained from the laser light source of the first and second wavelengths are each divided into two, and each pair of lasers is divided. A beam separating means for forming two pairs of light beams having two surfaces perpendicular to each other, and two pairs of light beams provided by the beam separating means.
A first optical means for intersecting at a point; a second optical means for collecting scattered light obtained when particles pass through the intersecting region; The light receiving area is divided into four light receiving areas, and the first and second light receiving areas and the first and third light receiving areas are divided so that they are adjacent to each other.
A first photoelectric converter that receives scattered light of the first and second wavelengths collected by the second optical means and converts the scattered light into an electric signal; and a first photoelectric converter collected by the second optical means. A second photoelectric converter for receiving scattered light of the first wavelength and converting it into an electric signal; and a third photoelectric converter for receiving scattered light of the second wavelength condensed by the second optical means and converting it into an electric signal. Photoelectric converter, first adding means for adding the outputs of the first and second light receiving regions of the first photoelectric converter which are adjacent to each other, and the third photoelectric converter of the first photoelectric converter which is adjacent to each other. A second adding means for adding the outputs of the fourth light receiving areas, a third adding means for adding the outputs of the first and third light receiving areas adjacent to each other of the first photoelectric converter, Fourth adding means for adding outputs of the second and fourth light receiving regions adjacent to each other of the first photoelectric converter, While the output is being obtained from the third photoelectric converter, the Y direction discriminating means for discriminating the direction based on the order of the outputs when the signals are successively obtained from the first and second adding means. And while the output is being obtained from the second photoelectric converter, when a signal is continuously obtained from the third and fourth adding means, the direction is discriminated based on the order of the outputs X Direction determining means, Y direction speed detecting means for detecting the speed in the Y direction from the frequency based on the output of the third photoelectric converter, and X frequency from the frequency based on the output of the second photoelectric converter. A laser velocity measuring device, comprising: an X-direction velocity detecting means for detecting a velocity in a direction.