JPH06308140A - Fiber type laser doppler flow meter - Google Patents

Abstract

PURPOSE:To measure flow rate in two-dimensional area by providing a mirror that reflects radiation light to a measurement point so that Doppler signal there is reflected to a photo- detection part and also a radiation part and a fixed part, mutually lacked in such a way they are allowed to move forward and backward in the direction of optical axis of the radiation light to the mirror. CONSTITUTION:The laser light from a laser oscillation device comes, through an optical fiber 4, into a laser radiation/Doppler signal photo-detection part 14, and then radiated by a lens 21, and further reflected on an aluminum-deposited surface 12 of a mirror 11, and then, through a window 17, a crossing paint 24 of the laser light 22 is formed at a speed measurement position in the fluid whose speed is to be measured. When a seed material that flows in the fluid together passes by a crossing point 24, the reflected light containing the Doppler signal issued when detecting the laser light 22 comes, through the window 17, into the mirror 11, and then is reflected and condensed on the photo-detection part 14. The light is introduced into a photomultiplier, and, through photoelectric conversion, comes into a signal process device, so that flow rate at the crossing point 24 is calculated. Alternately, by moving an outside tube 10 in the direction of axis and an inside tube 15 in the direction of axis accordingly, for the position of crossing point 24 to be changed in two-dimensional manner, flow rate may be measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber type laser Doppler velocimeter for measuring the flow velocity of a fluid relating to the performance of fluid machinery and the like.

[0002]

2. Description of the Related Art Documents (IMechE, J. Aerospace En
According to gineering, vol.205, no.1, p1-12), the laser from the laser emitting device is guided by two fibers to the laser emission part near the measurement part, and the two lasers from the emission part are mirrored. There is known a fiber-type laser Doppler anemometer that reflects the laser beams at different angles with each other to form an intersection of the two lasers in the measurement section and guides the Doppler signal from the fluid in the measurement section to the receiving fiber via the mirror. .

[0003]

However, in the laser Doppler velocimeter having such a structure, when the velocity distribution of the fluid sealed in the casing is measured by forming holes in the casing and inserting the velocimeter, There is a problem in that the flow velocity inside the fluid cannot be measured two-dimensionally, that is, the flow velocity at an arbitrary point within a certain plane cannot be measured, since this flow velocity meter can measure only the region moved back and forth (in the axial direction of the laser emitting part). is there.

An object of the present invention is to make it possible to measure a flow velocity in a two-dimensional area by moving a sensor in one direction in a fiber type laser Doppler velocimeter.

[0005]

SUMMARY OF THE INVENTION The above problem is that the two laser beams emitted in the axial direction from a sensor that moves forward and backward in the axial direction are reflected by a mirror toward a fluid whose velocity is to be measured at a predetermined angle. A fiber type laser Doppler velocimeter for intersecting the two laser beams at a measurement position in a velocity measurement target fluid and calculating a flow velocity of the velocity measurement target fluid at the measurement position using a Doppler signal generated from the intersection point. In the above, it is achieved by providing means for changing the distance between the sensor axis and the position where the two laser beams intersect.

As means for changing the distance between the crossing position of the two laser beams and the sensor axis, the two laser beams are radiated in the axial direction in order to cross the laser beams at the measuring position. When the two laser beams are directed in the directions intersecting with each other, a means for moving the radiating portion in the sensor axial direction may be provided.

In order to intersect the two laser beams at the measurement position, the two laser beams emitted in the axial direction are refracted by the emission lens and then reflected by the mirror. A means for moving the emitting lens in the sensor axial direction may be provided, and the emitting lens may be a zoom lens capable of changing its focal length.

[0008]

When the two laser beams emitted from the emitting unit in the sensor axial direction are directed in the directions intersecting with each other, the distance from the emitting unit to the intersecting position of the laser beams through the mirror is such that the laser beam is emitted from the emitting unit. It is uniquely determined by the angle and interval that they make when they are emitted from. Therefore, if the radiating portion is moved back and forth with respect to the mirror and the distance between the radiating portion and the mirror is changed, the distance between the mirror, that is, the position where the sensor axis intersects the laser beam changes accordingly.

When the two laser beams emitted from the emission section in the sensor axial direction are parallel to each other and are refracted by the emission lens in directions intersecting with each other, the laser beam passes from the emission lens through the mirror. The distance to the crossing position of is uniquely determined by the focal length of the emission lens and the distance between the laser light emitted from the emission portion. Therefore, if the emission lens is moved back and forth with respect to the mirror and the distance between the emission lens and the mirror is changed, the distance between the mirror, that is, the position where the sensor axis intersects the laser beam changes accordingly. Furthermore, if the focal length of the emission lens is changed, the distance from the emission lens to the crossing position of the laser light via the mirror changes accordingly, so that the distance between the emission lens and the mirror remains constant, The distance to the intersection of the mirror and the laser beam changes.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment according to the present invention will be described with reference to FIGS. FIG. 1 shows an outline of a flow velocity measuring system using a fiber-type laser Doppler flow velocity meter of this embodiment. The velocity meter shown in the figure is an oscillating device 1 for generating a laser beam such as an Ar-ion laser, and an optical fiber for transmitting the laser beam generated by the laser oscillating device 1 to a sensor unit inserted in a fluid 30 to be velocity-measured. 4, a coaxial biaxial traverse device 3 coupled to the sensor unit, a photomultiplier tube 6 coupled to the sensor unit via the coaxial biaxial traverse device 3 with an optical fiber 4A, and the photomultiplier tube 6 and a signal processing device 2 connected to the output side of the signal cable 5 by a signal cable 5.

The sensor portion includes a cylindrical outer cylinder 10 having a closed end, and a first intermediate cylinder 28 which is concentrically mounted inside the outer cylinder 10 at a distance from the inner peripheral surface of the outer cylinder 10. , A second intermediate cylinder 29 that is installed concentrically in the first intermediate cylinder 28 at a distance from the inner peripheral surface of the first intermediate cylinder 28, and a second intermediate cylinder 29 that is concentrically arranged in the second intermediate cylinder 29. The second intermediate cylinder 29 is internally mounted at a distance from the inner peripheral surface of the second intermediate cylinder 29, and is axially arranged with respect to the second intermediate cylinder 28 via two bearings 13 on the inner peripheral surface of the second intermediate cylinder 29. An inner cylinder 15 which is supported so as to move back and forth, and a laser emission / Doppler signal light receiving portion 14 which is installed at the tip of the inner cylinder 15.
Similarly, the laser beam is emitted from one end of the inner cylinder 15
Optical fibers 4, 4A connected to the Doppler signal light receiving unit 14 and the other end connected to the laser oscillator 1 and the photomultiplier tube through the coaxial biaxial traverse device 3.
The outer cylinder 10, the first intermediate cylinder 28, and the second intermediate cylinder 29 are attached at their distal ends to openings formed so as to communicate the inside of the second intermediate cylinder 29 with the outside of the outer cylinder 10. A window 17 made of quartz glass, and a mirror that is installed at the tip of the second intermediate tube 29 and reflects the laser emitted from the laser emission / Doppler signal light receiving section 14 toward the outside of the outer tube through the window. 11 is included. The reflecting surface of the mirror 11 is an aluminum vapor-deposited surface 12 and is arranged so as to reflect the emitted laser light 22 at right angles to its optical axis.

FIG. 4 shows a structural example of the laser emission / Doppler signal light receiving portion 14. The laser emitting / Doppler signal receiving section 14 is a laser emitting section 18 for emitting two laser beams.
And a Doppler signal light receiving portion 19 for receiving the reflected light are integrally formed, and the tip end thereof has a focal length Ft for refracting the emitted two parallel laser beams to converge at the measurement position. 21 and the light receiving lens 20 are mounted.

The outer cylinder 10, the first intermediate cylinder 28, and the second intermediate cylinder 29 are fixed so as not to move with each other, and the tip of the second intermediate cylinder 29 is closed.
An opening that connects the inside and the outside of the first intermediate cylinder 28 is provided at the tip of the first intermediate cylinder 28. Between the second intermediate cylinder 29 and the first intermediate cylinder 28, and the first intermediate cylinder 28
A flow path for the refrigerant 16 is formed between the outer cylinder 10 and the outer cylinder 10. Second
The refrigerant is sent from the coaxial two-axis traverse device 3 side on the right side in the drawing into the refrigerant flow path between the intermediate cylinder 29 and the first intermediate cylinder 28, and this refrigerant is opened at the tip of the first intermediate cylinder 28. Flows into the refrigerant flow path between the first intermediate cylinder 28 and the outer cylinder 10,
The outer cylinder 10 is cooled from the inner surface while returning from the tip of the outer cylinder 10 to the coaxial biaxial traverse device 3 side. By this cooling,
The sensor unit can be used for measurement in high temperature fluid.

FIG. 7 shows the configuration of the coaxial biaxial traverse device 3. The coaxial two-axis traverse device 3 is airtightly fitted and fixed to the side of the opening formed in the casing 31 where the fluid to be measured does not exist, and the cooling flange 31 having the outer cylinder 10 axially movably inserted thereinto. And four bolts 38 fixed to the cooling flange 31 in parallel with the axis of the outer cylinder 10.
And the outer cylinder drive unit 3 that moves along the four bolts 38.
3, a fixing plate 34 fixed to the end portions of the bolts 38 to prevent movement between the bolts 38, an outer cylinder flange 35 fixed to the outer periphery of the rear end of the outer cylinder 10, and the outer cylinder flange 35. Four bolts 39 fixed parallel to the axis of the outer cylinder 10, an inner cylinder drive unit 36 that moves along the four bolts 39, and a bolt 39 fixed to the end of the bolt 39.
It is configured to include a fixing plate 37 that restrains movement between them. The fixed plate 34 is provided with an opening at the center thereof having a size through which the inner cylinder drive unit 36 can pass.

The four bolts 38 are respectively arranged at the positions forming the apexes of a quadrangle, and two of the four bolts 38 which are diagonal to each other are ball-screwed. Outer cylinder drive unit 3
The reference numeral 3 designates a drive plate fixed to the outer peripheral surface of the outer cylinder 10 through which the outer cylinder 10 is inserted through the central opening and a ball screwed bolt 38, which is screwed to the drive plate. A ball screw nut that is restrained from moving in the axial direction and is rotatably engaged with the periphery of the bolt 38, and two ball screws 38 that are not cut with the ball screw are slidably inserted and the drive plate is provided. And two externally fixed bearings, and an outer cylinder driving stepping motor that is mounted on the drive plate to rotate the ball screw nut around the bolt 38. When the outer cylinder driving stepping motor rotates the ball screw nut around the bolt 38, the drive plate moves along the bolt 38 as the ball screw nut rotates. Since the drive plate is fixed to the outer cylinder 10, as the drive plate moves, the outer cylinder 10
Also moves back and forth with respect to the cooling flange 32, in other words, with respect to the fluid 30 to be measured.

The four bolts 39 and the inner cylinder drive unit 36 also have the same structure as the four bolts 38 and the outer cylinder drive unit 33, and the inner cylinder 15 and the outer cylinder 10 are driven by the inner cylinder drive stepping motor. It is configured to move back and forth against.

The operation of the apparatus having the above structure will be described below with reference to FIGS. Laser light such as an Ar-ion laser generated and emitted by the laser oscillator 1 is guided to the laser emission / Doppler signal light receiving section 14 by the optical fiber 4, and refracted and emitted by the emission lens 21. Although the optical fiber 4 is shown by one line in the figure, two laser beams are actually guided. The light emitted from the laser emission / Doppler signal receiving portion 14 is the aluminum vapor deposition surface 12 of the mirror 11.
At the velocity measurement position in the fluid 30 to be velocity-measured through the window 17, the intersection point 24 of the laser light 22 is formed.
The focal length of the emission lens 21 is Ft, and the emission lens 21 is
If the distance between the mirror 11 and the mirror 11 is Fl2, the distance between the mirror 11 and the intersection 24 is Fl1, as shown in FIG.
It is shown by Fl1 = Ft-Fl2.

The seed material flowing in the fluid 30 to be velocity-measured following the movement of the fluid is the intersection point 24 of the laser light.
The reflected light including the Doppler signal emitted by receiving the laser light when passing through the laser beam enters the mirror 11 through the window 17,
The light is reflected by the mirror 11 and focused on the laser emission / Doppler signal receiving unit 14. The condensed reflected light is guided to the photomultiplier tube 6 by the optical fiber 4A and converted into an electric signal. This electric signal is sent to the signal processing device 2 via the signal cable 5, is subjected to processing such as Fourier transform, and the velocity of the fluid at the intersection 24 is calculated from the frequency of the Doppler signal.

The measurement point is changed by moving the outer cylinder 10 having the inner cylinder 15 in the axial direction by the coaxial two-axis traverse device 3 and moving the inner cylinder 15 in the axial direction with respect to the outer cylinder 10. This is realized by changing the distance between the emission lens 21 and the mirror 11 from Fl2 to Fs2 as shown in FIG. The movement of the outer cylinder 10 in the axial direction changes the distance from the casing 31 at the intersection point 24, which is the measurement position. Further, by moving the inner cylinder 15 forward and backward with respect to the outer cylinder 10 and changing the distance between the emission lens 21 and the mirror 11 from Fl2 to Fs2, the distance between the mirror 11 and the intersection 24 is Fs1 = Ft−. Change to Fs2. That is, by moving the outer cylinder 10 that houses the inner cylinder 15 back and forth in the axial direction and moving the inner cylinder 15 back and forth in the axial direction with respect to the outer cylinder 10, the position of the intersection point 24 within the velocity measurement target fluid 30. It is possible to measure the two-dimensional velocity distribution of the velocity measurement target fluid 30 by changing it two-dimensionally.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, the mirror 11 is arranged so that the reflection angle for reflecting the emitted laser light is larger than 45 degrees, and the window 17 is provided.
The position and the inclination are changed accordingly, and the other components are the same as those in the first embodiment. According to the present embodiment, the same effect as that of the first embodiment can be obtained, and the intersection point 24 of the laser light can be formed further on the left side in the drawing than the tip of the outer cylinder 10. Therefore, as shown in FIG. 1, when the velocity measurement target fluid 30 flows from the left side to the right side in the drawing, the outer cylinder 10, that is, the sensor has less influence on the flow state of the velocity measurement target fluid 30, A two-dimensional flow velocity distribution can be measured on the upstream side.

FIG. 6 shows another example of the structure of the window 17 of the first embodiment. The optical fibers 4 and 4A and the laser emission / Doppler signal light receiving portion 14 are bonded with an adhesive, but the strength of this bonding portion is likely to decrease at high temperatures. The example shown in FIG. 6 considers a case where the outer cylinder 10 is exposed to a high-temperature, high-pressure velocity measurement target fluid, and the outer cylinder 1 is surrounded by the window 17.
No. 0 and the inside of the second intermediate cylinder 29 are provided with a plurality of small holes 40, and the inner cylinder 15 is provided near the joint between the optical fibers 4, 4A and the laser emission / Doppler signal receiving section 14 on the wall surface of the inner cylinder 15. An opening for communicating the inside and the outside is provided. With this configuration, the fluid 3
Cryogenic fluid at a pressure slightly above zero, eg air, is introduced. The introduced air flows through the inner cylinder 15 and the optical fibers 4, 4A and the laser emission / Doppler signal receiving section 14
The joint is cooled, and the pressure difference with the high-pressure fluid on the outside is reduced to improve the strength reliability of the structure. The air that has cooled the joint portion flows out of the inner cylinder and further flows through the small holes 40 to the surface of the window 17 to prevent fogging of the window 17 and prevent deterioration of the laser beam transmission performance.

FIG. 8 shows an example in which the present invention is applied to the velocity measurement of each part of the combustion flame of a boiler burner. In this example, it is possible to measure the flow velocity of each part of the flame in the two-dimensional plane of the blowing direction of the burner and the direction perpendicular to this blowing direction, and it becomes easy to collect data for combustion analysis.

FIG. 9 shows an example in which the present invention is applied to the measurement of the outlet flow velocity distribution of the gas turbine stationary blade 41. In this example, the velocity distribution of the combustion gas in the two-dimensional region in the longitudinal direction of the turbine shaft and the radial direction of the turbine shaft can be measured by moving the outer cylinder 10 and the inner cylinder 15 back and forth independently of each other. Data collection for design becomes easy.

In each of the above embodiments, the sensor only moves back and forth in the axial direction, but the sensor may be further rotated around the axis. For example, the portions of the drive plates of the outer cylinder drive unit 33 and the inner cylinder drive unit 36 of the coaxial two-axis traverse device 3 shown in FIG. 7 that are fixed to the outer cylinder 10 and the inner cylinder 15 are formed into another disk shape. The disk-shaped portion fixed to the outer cylinder 10 and the inner cylinder 15 are separated from each other and rotatably around the axis of the inner cylinder 15 and fixed to the other part of the drive plate in the axial direction. A rotating stepping motor that rotates the fixed disk-shaped portion in synchronization is provided. By doing so, the velocity measurement range can be expanded to a three-dimensional region, and it becomes easy to measure a non-axisymmetric flow state.

Further, in each of the above-described embodiments, the distance between the radiation lens 21 and the mirror 11 is changed in order to change the distance between the mirror 11 and the intersection 24. Therefore, the measurement range in the direction perpendicular to the outer cylinder 10 is It is proportional to the moving distance of the inner cylinder 15. On the other hand, in order to change the distance between the mirror 11 and the intersection 24,
The focal length of the emission lens 21 may be changed. For example, the radiation lens 21 is a zoom lens,
By changing the focal length of the emission lens 21, the distance between the mirror 11 and the intersection 24 can be changed without changing the distance between the emission lens 21 and the mirror 11. According to this configuration, the focal length can be changed 3 to 4 times, and the measurement range in the direction perpendicular to the outer cylinder 10 can be expanded regardless of the moving length of the inner cylinder.

Further, in each of the above-described embodiments, the emission lens 21 is fixed to the laser emission / Doppler signal light receiving portion 14, but the emission lens 21 and the laser emission / Doppler signal light receiving portion 14 are separated from each other, and the laser The same effect can be obtained by fixing the radiation / Doppler signal light receiving unit 14 and moving the radiation lens 21 in the optical axis direction.

[0027]

According to the present invention, by moving the laser light emitting / Doppler signal light receiving portion by the optical fiber in the axial direction of the sensor portion, and by moving the emitting lens in the axial direction of the sensor portion, Furthermore, by changing the focal length of the emission lens, it becomes possible to measure the two-dimensional flow velocity distribution of the fluid by using the reflection of the laser light by the mirror, and the two-dimensional accuracy of the flow velocity measurement is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a partial sectional view showing details of a portion of the embodiment shown in FIG.

FIG. 3 is a partial cross-sectional view showing another state of the portion shown in FIG.

FIG. 4 is a partial sectional view showing details of a portion of the embodiment shown in FIG.

FIG. 5 is a partial sectional view showing a second embodiment of the present invention.

FIG. 6 is a partial cross-sectional view showing details of another portion of the embodiment shown in FIG.

FIG. 7 is a partial cross-sectional view showing details of another portion of the embodiment shown in FIG.

FIG. 8 is a cross-sectional view showing an application example of the device of the present invention.

FIG. 9 is a cross-sectional view showing another application example of the device of the present invention.

[Explanation of symbols]

 1 Laser oscillation device 2 Signal processing device 3 Coaxial 2-axis traverse device 4, 4A Optical fiber 5 Signal cable 6 Photomultiplier tube 10 Outer cylinder 11 Mirror 12 Aluminum vapor deposition surface 13 Bearing 14 Laser emission / Doppler signal receiving section 15 Inner cylinder 16 Refrigerant 17 Window 18 Laser Light Emitting Section 19 Doppler Signal Receiving Section 20 Receiving Lens 21 Emitting Lens 22 Laser Emitting Light 23 Doppler Signal 24 Laser Light Crossing Point 26 Heat Resistant Seal 27 High Pressure / Low Temperature Air 28 First Intermediate Tube 29 Second Intermediate cylinder 30 Fluid for speed measurement 31 Casing 32 Cooling flange 33 Outer cylinder drive part 34 Fixing plate 35 Outer cylinder flange 36 Inner cylinder drive part 37 Fixing plate 38 Bolt 39 Bolt 40 Small hole 41 Turbine vane

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeru Shodohata 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (6)

[Claims] 1. A laser oscillated by a laser oscillating device is guided to a laser emitting section by an optical fiber, two lasers emitted from the laser emitting section are crossed at a measurement position of a fluid to be measured, and the crossing point is passed. Receive the Doppler signal generated from the fluid to be measured or solid particles in the fluid to be measured by a light receiving unit arranged in the vicinity of the laser emitting unit, convert the received Doppler signal into an electric signal, and input the electric signal In the fiber laser Doppler velocimeter for determining the flow velocity of the measurement target fluid or the solid particles in the measurement target fluid in the signal processing device, a laser emitting unit that emits the laser and a light receiving unit that receives the Doppler signal are fixed to each other, The laser emitted from the laser emitting unit is reflected to the measurement position and the Doppler signal from the measurement position is reflected. A mirror for reflecting the signal to the light receiving portion is arranged, and the fixed laser emitting portion and light receiving portion are configured to be capable of advancing and retreating in the optical axis direction of the laser light emitted to the mirror. Fiber type laser Doppler velocity meter. 2. The fiber type laser Doppler velocimeter according to claim 1, wherein the laser emitting portion is provided in a tubular body having a window portion for transmitting the laser light reflected by the mirror and the Doppler signal from the measuring portion. A fiber-type laser Doppler velocimeter including a light-receiving unit and a mirror, and having means for moving the cylindrical body forward and backward in the optical axis direction of the laser light emitted from the laser emission unit. 3. A laser oscillating device for oscillating a laser, an optical fiber for transmitting the laser, and a laser transmitted by the optical fiber for radiating at least two parallel light beams, and at least two parallel laser beams. A laser emission part having a radiation lens for converging at a measurement position in the fluid to be measured, and a Doppler signal incident from the measurement position while reflecting the laser light emitted through the emission lens toward the measurement position. A cylindrical body having a mirror for reflecting light including the reflected light toward a light receiving portion, a window portion that incorporates the laser emitting portion, the light receiving portion, and the mirror, and transmits the laser reflected toward the measurement position by the mirror. A traverse means for moving the tubular body forward and backward with respect to the fluid to be measured in the axial direction of the tubular body; a means for converting light received by the light receiving section into an electric signal; In a fiber type laser Doppler velocimeter including a signal processing means for calculating a flow velocity of a fluid to be measured or a solid particle in the fluid to be measured with an electric signal as an input, a laser emitting portion emitting the laser and a Doppler signal are received. The fiber type laser Doppler, wherein the light receiving section is fixed to each other, and the laser emitting section and the light receiving section which are fixed to each other are configured to be movable back and forth in the optical axis direction of the laser light emitted to the mirror. Anemometer. 4. A laser oscillating device for oscillating a laser, an optical fiber for transmitting the laser, a laser transmitted by the optical fiber for radiating at least two parallel rays, and at least two parallel lasers. A laser emission part having a radiation lens for converging at a measurement position in the fluid to be measured, and a Doppler signal incident from the measurement position while reflecting the laser light emitted through the emission lens toward the measurement position. A cylindrical body having a mirror for reflecting light including the reflected light toward a light receiving portion, a window portion that incorporates the laser emitting portion, the light receiving portion, and the mirror, and transmits the laser reflected toward the measurement position by the mirror. A traverse means for moving the tubular body forward and backward with respect to the fluid to be measured in the axial direction of the tubular body; a means for converting light received by the light receiving section into an electric signal; In a fiber type laser Doppler velocimeter including a signal processing means for calculating a flow velocity of a fluid to be measured or a solid particle in the fluid to be measured with an electric signal as an input, the emission lens has its optical axis relative to the mirror. A fiber-type laser Doppler velocimeter characterized by being configured to move forward and backward. 5. A laser oscillating device for oscillating a laser, an optical fiber for transmitting the laser, radiating the laser transmitted by the optical fiber as at least two parallel rays of light, and the at least two parallel lasers. A laser emission part having a radiation lens for converging at a measurement position in the fluid to be measured, and a Doppler signal incident from the measurement position while reflecting the laser light emitted through the emission lens toward the measurement position. A cylindrical body having a mirror for reflecting light including the reflected light toward a light receiving portion, a window portion that incorporates the laser emitting portion, the light receiving portion, and the mirror, and transmits the laser reflected toward the measurement position by the mirror. A traverse means for moving the tubular body forward and backward with respect to the fluid to be measured in the axial direction of the tubular body; a means for converting light received by the light receiving section into an electric signal; In a fiber type laser Doppler velocimeter including a signal processing means for calculating a flow velocity of a fluid to be measured or a solid particle in the fluid to be measured with an electric signal as an input, the radiation lens is a zoom lens having a changeable focal length. A fiber type laser Doppler velocimeter characterized by: 6. The fiber type laser Doppler velocimeter according to claim 1, wherein the laser emitting section, the mirror and the light receiving section have an optical axis of laser light emitted from the laser emitting section. A fiber type laser which is configured to be rotatable about a center and has a driving unit that rotates a laser emitting portion, a mirror, and a light receiving portion in synchronization with each other about an optical axis of laser light emitted from the laser emitting portion. Doppler anemometer.