JPS60102563A - Laser doppler speedometer - Google Patents

Abstract

PURPOSE:To reduce a measuring error to the variation in the distance from the leading end of a probe to an object to be measured, by adding convex lenses in front of two beam transmitting optical probes and reducing the expanse angle of the beam emitted from each beam transmitting optical probe in the vicinity of the measuring region of the object to be measured. CONSTITUTION:Incident laser beam is split into two beams by a beam splitter 3 while the split beams enter two beam transmitting optical probes 15. Each probe 15 is constituted by adding a micro-lens 5 to the leading end of an optical fiber 2 and integrating the same with the convex lens 6 added thereto by a support 7. In this case, beams are emitted from the beam transmitting optical probes 15 as almost parallel beams. Scattered beams to emitted beams are subjected to heterodyne detection by a beam detector 12 while beam received by a beam receiving probe 16 is transmitted by the fiber 2 to be guided to the beam detector 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a laser Doppler velocimeter that detects the speed of iatu regular holidays using laser light.

[Prior art]

A conventional Yuzu laser Doppler velocimeter is shown in Figure 1. Figure 1 schematically shows a conventional laser Doppler velocimeter (/4 formation 1a).
1 is a laser light source, 2 is an optical fiber, 3 is a beam splinter that distributes the laser beam, 5 is a microlens, 4 is a light transmitting moonlight globe that integrates the microlens 5 and the optical fiber 2, 8 is a cover 6 for fluid, etc. (Closed, 91'i scattered light particles, 11 is a light receiving optical probe with a microlens 5 added to the optical fiber 2, 12 is an APIJ (avalanche photodiode).

)' INPIJ (bin photodiode), photodetector with photomultiplier tube, 13 is an optical receiver consisting of a front ILJ amplifier, a bandpass filter, a main amplifier, etc., 14V-J
, '7'o-fu (^1 This is a regular jig.

Next, the operation shown in FIG. 1 will be explained. Laser light emitted from the laser light source l enters the optical fiber 2. This incident laser light is split into two parts by the beam splitter 3, and -2 light transmitting light loafs e (2
For light transmission of books, the emitted light from the optical noloaf 4 ttJ, handling d
(1) Closed within 8-C We are waiting for each other's parents to stay for a long time. 1. This IC, this intersection is a scattered light moving at speed! V
Child 9 Kareret Yu, nine, the Truffler effect 4 is received - (scattered δ is generated. Of this scattered light, the scattered light can be received by the light flow 11. The received light is transmitted through the optical fiber. 2 and guided to the photodetector 12.The scattered light appearing in the light emitted from the two light-transmitting moonlight globes 4 has received different amounts of top-sheath shift, and these scattered lights are detected by photodetection. The p-heteroton is detected by the detector 12. The detection frequency f in this case is expressed by equation (1) below.

2nV above, 0 Here, n is the curve of the fixed holiday 8 ↓], λ is the wavelength of light in vacuum, θ is the intersection angle of the two incident beams, and Vl is the optical axis of the two output beams. The velocity V in the direction perpendicular to the perpendicular bisector of
It is a component of The detection frequency f is set to 1 using the above equation (1).
1111 can be determined by knowing the speed v1.

Using the conventional optical fiber 2, the six-rate Tzufler movement t
l is 47 + j as shown above and Jt is 10,'? ,
r Change the distance at 8t from the tip of each light transmitting glove 4 to an IC with a 1 mm υ angle of the output light from the light transmitting sunlight globe 4. I was faced with the drawback that the 61-year-old regular school fee difference was getting bigger. In other words, in Figure 2) J<-
If the wide 9 angles of the emitted light from each light-transmitting moonlight globe 4 are α, then the areas a and b where the two emitted lights intersect.

Each detection frequency ja when there is a constant n+++ constant 8 in C
+fb, fc+-jh, respectively - (2), (3
J, (represented by the 4J formula.

2rtVl, (1+(t j'a---1λ-stn了-・・・・・・・・・River・
...(2)2+1V1. θ fb=−−−−sm−−−−・・・・・・・・・・・・
...(3) λ2 2nVlo-α fc=−−−−−−λ5ln−2−・・・・・・・・・
(4) In this way, as the position of the object to be measured 8 changes, the detected detection frequency j changes, for example, as shown in equations (2) to (4) above. This has the disadvantage that accurate measurement results cannot be obtained.

[Departure No. 114] The older brother's idea was to improve the above-mentioned drawbacks of the conventional one, with a convex lens 'lr on the opposite side of the two light transmitting globes. (=41+ where J is added and the wide angle of the emitted light from each light transmitting light 70-p is made smaller in the vicinity of the constant area 61 of the liquid emitting u constant) Formation f:' 4-J shi,
The present invention provides a laser Doppler velocimeter that can calculate the total AT11 constant error due to changes in the distance from the tip of each light-transmitting moonlight globe to the object to be measured.

Example of L firing ψ] Embodiments of the invention will now be described with reference to the drawings.

Figure 3 shows a laser draft sheet that is an example of this emission ψ.
The speed d1 is indicated by 41, which is a schematic configuration diagram, and the same parts as those in FIG. In the figure, 6.10 is a convex lens, 7 is a support body that supports each convex lens 6.10i, and 151
Yu convex lens 6. Microlens 5. Optical fiber 2 -9
・An optical probe for light transmission with 11 elements, 1tlL convex lens 1υ, microlens 5 gold optical fiber 2, and 7 other light-receiving optical probes are the same as those shown in Figure 1 above. It is composed of

Next, the operation shown in FIG. 3 will be explained. Laser light emitted from a laser light source 1 enters an optical fiber 2.

This incident laser light is split into two by the beam splitter 3.
The light is distributed and placed into two light transmitting optical globes 15.

Each light transmitting optical globe 15 has a structure in which a microlens 5 is added to the tip of the optical fiber 2, and a convex lens 6 is added to the support 7 to integrate it, and the microlens 5 is a convex lens. The straight edge is located near the focal point of No. 6.

The emitted light from each light transmitting optical globe 15 is emitted as a parallel beam el, and these emitted lights are, as shown in FIG.
The beam waists BW are formed within the object to be measured 8 and are designed to intersect with each other. Therefore, if the scattered light particles 9 move at this intersection at the speed 2, the light will be scattered by the Doppler effect. Of this scattered light, the backscattered light is received by the light receiving optical probe 6. Optical probe 16 for light reception and L'iC company, ■An optical fiber 2 whose end is simply sharply polished, ■An optical fiber 2 with a microlens 5 added, ■A convex lens that converts scattered light into parallel light, A focusing lens that focuses this parallel light beam onto the end face of the tip fiber 2 and a structure composed of the optical fiber 2 are used, respectively. Make it look like it's going away.

The light receiving light 70 - the light t received by the beam 16 and the optical fiber 2
and is detected by the photodetector 12.

Scattered light incident on the output light from the two light transmitting moonlight beams 70 and 15 has different Doppler shift amounts, and these scattered lights are heterotine-detected by the photodetector 12. The detection frequency f is expressed by the above equation (1) at any point in the area where the lights emitted from the two light transmitting optical globes I5 intersect (the point in the area aI+bIrCI shown in FIG. 4). This is because, as shown in FIG. 4, a beam waste (BW) is formed in the intersecting region. Therefore, since a photocurrent with a detection frequency j flows through the photodetector 12, this photocurrent is amplified by the optical receiver 13, and frequency analysis is performed using a frequency analyzer (not shown), a 4V converter, a frequency tracker, etc. as described above. It is possible to know the velocity vLt- from the equation (1).

In addition, in the second embodiment, the light receiving globe 16 is installed between the two light transmitting moonlight globes 15, but it can also be installed outside the two light transmitting moonlight globes 5. The two light transmitting optical globes 15 and the light receiving optical globes 16 do not have to be in the same plane.

Further, in the above embodiment, a fluid is used as an example of the object to be measured 8, but it may be a moving object such as a rotating or translating object.

Further, in the above embodiment, the optical fiber 2 installed between the laser beam ti+1 and the beam spacer 9 230 is used, or a narrow space may be used instead.

Further, the two light transmitting optical globes 15 and the light receiving optical globes 16 and O in the above embodiment may be fixed together in a jig or the like.

Further, in the above embodiment, the light-receiving optical globe 16 that receives scattered light is used, but instead of this, an API (API) or the like may be used to receive light at 1μ contact.

Furthermore, in the above embodiment, the case where backscattered light among the scattered light is received is shown, but as shown in FIG. good.

〔Effect of the invention〕

As explained above, this invention adds a convex lens to the left side of the two light transmitting optical globes in the laser beam speed system, and widens the output light from each light transmitting light 70-power. Since the p angle is configured to be small near the measurement area of the object to be measured, it is possible to extremely reduce measurement errors caused by fluctuations in the distance from the tip of each light transmitting moonlight globe to the object to be measured. This has an excellent effect.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing the Laser Dotsfler speedometer from UL (
Figure 2 is the 118th! ! , l's laser dots'
Figure 3 shows the laser Doppler speed J1, which is an example of -dog m + of this origin, and Figure 4 shows the small-scale fall configuration diagram. Laser Drafuji in Figure 3 - speed i, lpL movement 3' and 1-like sword explanation 1, Figure 5 shows the fruit of this light j
FIG. 2 is an explanatory diagram showing the operation mode of a Laser-Dotsfler speedometer according to an example. In the figure, 1... Layer photoelectric, 2... Optical fiber, 3... Beam splitter, 4.15... Optical globe for light transmission, 5... Micro lens, 6.10... Convex lens. , 7...44 supports, 8...m? ltu constant,
Fixed body...scattered light particles, 11° 16... light receiving light globe, 12... photodetector, 13... optical receiver, 14...
...Glove fixing jig. In each figure, the same reference numerals indicate the same or equivalent parts. Agent Masu Oiwa Figure 1-8 Figure 2-4 Figure 3 Figure 4

Claims (1)

[Claims] - A laser light source that does not emit any laser light, a beam splitter that can distribute the laser light, two light transmitting globes that integrate a convex lens, a microlens, and an optical fiber, and a light receiving array. j element 70-b and a photodetector ft'
Set the emitted light from the light transmitting Wako probe in D'l 2/g so that it intersects at j9 + constant area, and ? 111j Scattered light by constant body & 11
1) A recording light receiver is transmitted to one device, and the speed of the target jtll is detected by a loli recording photodetector based on the amount of dog-sea shift that differs depending on the intersection of the scattered light. Laser troughler speed meter.