JPH0447266B2 - - Google Patents
Info
- Publication number
- JPH0447266B2 JPH0447266B2 JP23672786A JP23672786A JPH0447266B2 JP H0447266 B2 JPH0447266 B2 JP H0447266B2 JP 23672786 A JP23672786 A JP 23672786A JP 23672786 A JP23672786 A JP 23672786A JP H0447266 B2 JPH0447266 B2 JP H0447266B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- frequency
- measured
- difference
- scattered
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 230000003287 optical effect Effects 0.000 claims description 25
- 238000005259 measurement Methods 0.000 description 8
- 238000001514 detection method Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000013307 optical fiber Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000012530 fluid Substances 0.000 description 3
- 239000000835 fiber Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
Landscapes
- Optical Radar Systems And Details Thereof (AREA)
Description
【発明の詳細な説明】
「従来の技術」
光ドツプラー速度計は主にレーザ光を使用し、
レーザ光を移動物体に照射し、その物体からの散
乱光の周波数が、ドツプラー効果によりシフトす
ることを利用し、移動速度を測定する。特徴とし
ては、非接触、広帯域、高速応答、高空間分解能
などが挙げられる。第３図に従来のレーザードツ
プラー速度計のうちで光学系に光フアイバーを使
用したものの代表例を示す。レーザー１から出た
周波数f0の光はビームスプリツター２で２つに分
けられ、一方はミラー３をとおりレンズ５により
光フアイバー６中に導入される。他方の光は周波
数シフター４をとおり、周波数f0＋Δf（Δfは周波
数シフター４によるシフト量）となつてレンズ
５′により送光用光フアイバー６′中に導入され
る。それぞれの光はフアイバー６，６′を通つて
移動物体（流体中の散乱粒子等）に照射される。
照射光が交叉する交叉領域中の移動物体で散乱さ
れた光は、その速度に応じてドツプラー効果を受
け周波数fdだけシフトしている。ここにおいてfd
は
fd＝Ｖ／λsinθ／２
で表わされる。しかしλはレーザー光の波長で
Ｃ／f0に等しい（Ｃは光速）。θは２つの入射光
の交差角である。散乱された光のうち、一部が受
光用フアイバー８に入る。８に入る光のうち６か
ら出たものについては、f0＋fd，６′から出たも
のについては、f0＋Δf−fdとなつている。この２
つの光が受光素子９上でヘテロダイン検波され、
その差成分すなわち2fd−Δfのみ電気信号として
取り出される。この信号を周波数分析することに
より、移動物体の速度Ｖを知ることができる。１
０はこの周波数分析を行い速度を求める信号処理
装置である。なお送光用光フアイバー６，６′は
第３図に示すように流管１３の縦方向の管壁に対
してαの角度を持つように設定されそれぞれ流管
内の流れに逆う向き又は流れに沿う向きに光が照
射される。[Detailed description of the invention] "Prior art" Optical Doppler velocimeters mainly use laser light,
A moving object is irradiated with a laser beam, and the moving speed is measured by utilizing the fact that the frequency of the scattered light from the object shifts due to the Doppler effect. Features include non-contact, broadband, high-speed response, and high spatial resolution. FIG. 3 shows a typical example of a conventional laser Doppler velocimeter that uses an optical fiber in its optical system. Light having a frequency f 0 emitted from a laser 1 is split into two by a beam splitter 2, and one passes through a mirror 3 and is introduced into an optical fiber 6 by a lens 5. The other light passes through the frequency shifter 4, becomes a frequency f 0 +Δf (Δf is the amount of shift by the frequency shifter 4), and is introduced into the light transmitting optical fiber 6' by the lens 5'. Each light passes through fibers 6 and 6' and is irradiated onto a moving object (scattered particles in a fluid, etc.).
The light scattered by the moving object in the intersection region where the irradiated light intersects is affected by the Doppler effect and shifted by the frequency f d according to its speed. Here f d
is expressed as f d =V/λsinθ/2. However, λ is the wavelength of the laser beam and is equal to C/f 0 (C is the speed of light). θ is the intersection angle of the two incident lights. A portion of the scattered light enters the light receiving fiber 8. Of the light that enters 8, the light that comes out from 6 is f 0 +f d , and the light that comes out from 6' is f 0 +Δf - f d . This 2
The two lights are heterodyne detected on the light receiving element 9,
Only the difference component, 2f d −Δf, is extracted as an electrical signal. By frequency-analyzing this signal, the speed V of the moving object can be determined. 1
0 is a signal processing device that performs this frequency analysis and determines the speed. The light transmitting optical fibers 6 and 6' are set at an angle α with respect to the vertical wall of the flow tube 13, as shown in FIG. Light is emitted in the direction along.
「従来技術の問題点」
測定対象が流体であるとき、場所によつて速度
分布があることがある。このような場合ヘテロダ
イン検波して得られる信号は周波数分布を持つ。
これは第４図に示したように入射ビームの交差し
た領域７が交叉領域であり、有限の大きさを持つ
ていてこの中の場所によつて異なる速度の散乱粒
子が存在するからである。第５図のようにヘテロ
ダイン検波した信号は周波数分布を持つ。光をレ
ンズ系などによりしぼりこめば領域７を小さくす
ることができ、第６図のように細い周波数分布を
もたせるように空間分解能を高めることができ
る。しかしながら、場所の制約によりレンズをお
けない、あるいはレンズでしぼりこむのに限界が
あるなど、かならずしも空間分解能を望ましい値
に迄高めることができない。特に細い管内を流れ
る流体などの場合、急激な速度分布を伴つてお
り、第５図に示したように、検波した信号に周波
数分布ができるので局所的な速度分布を求めるこ
とができない。"Problems with the Prior Art" When the object to be measured is a fluid, there may be a velocity distribution depending on the location. In such a case, the signal obtained by heterodyne detection has a frequency distribution.
This is because, as shown in FIG. 4, the area 7 where the incident beams intersect is an intersection area, which has a finite size and in which scattered particles exist with different velocities depending on their location. As shown in FIG. 5, the heterodyne detected signal has a frequency distribution. By concentrating the light using a lens system or the like, the area 7 can be made smaller, and the spatial resolution can be increased to provide a narrow frequency distribution as shown in FIG. However, it is not always possible to increase the spatial resolution to a desired value because the lens cannot be placed due to space constraints, or there is a limit to how narrow the lens can be. Particularly in the case of fluid flowing in a narrow pipe, the velocity distribution is abrupt, and as shown in FIG. 5, the detected signal has a frequency distribution, making it impossible to determine the local velocity distribution.
この発明の目的は、光ドツプラー速度計の空間
分解能を高め、局所的な速度分布も正確に測定可
能ならしめることである。 The purpose of this invention is to improve the spatial resolution of an optical Doppler velocimeter and to enable accurate measurement of local velocity distribution.
「問題点を解決するための手段」
この発明によれば光ドツプラー速度計の光源と
してレーザーに代つてコヒーレンス長が数μm乃
至数＋μmの低コヒーレンス光源が用いられると
共に被測定体に照射する２つの照射光の光路長に
差を与えることができる光路長調整手段が設けら
れる。"Means for Solving the Problem" According to the present invention, a low coherence light source with a coherence length of several μm to several + μm is used instead of a laser as the light source of an optical Doppler velocimeter, and two Optical path length adjusting means is provided that can give a difference to the optical path length of the irradiated light.
このように低コヒーレンス光源を用いると、２
つの照射光が交叉する交叉領域内の光路長がたか
だかコヒーレンス長だけ相違する狭い領域のみの
２つの散乱光が干渉し、ヘテロダイン検波により
２つの散乱光の差の周波数を持つ信号を得ること
ができる。また上記光路長調整手段によつてその
測定可能な領域を被測定体の流れの方向に調整す
ることができるので測定可能な領域を増々小さく
設定することができる。従つて、光ドツプラー速
度計の空間分解能を従来より高め、局所的な速度
分布も正確に測定できるようになる。 When using a low coherence light source in this way, 2
Two scattered lights in a narrow region where the optical path lengths in the intersection region where the two irradiated lights intersect differ at most by the coherence length interfere, and heterodyne detection can obtain a signal with a frequency that is the difference between the two scattered lights. . Further, since the measurable area can be adjusted in the direction of flow of the object to be measured by the optical path length adjusting means, the measurable area can be set smaller and smaller. Therefore, the spatial resolution of the optical Doppler velocimeter is improved compared to the conventional one, and local velocity distribution can also be accurately measured.
「実施例」
この発明の実施例を第１図に示す。第３図の従
来例と対応する部分には同じ符号を付して重複説
明は省略する。第３図と異なる点は光源としてコ
ヒーレンス長が数μm〜数＋μmの低コヒーレンス
光源２０を用いた点とビームスプリツター２とミ
ラー３との間の距離を調整できる光路長差調整手
段２１を設けた点である。このような低コヒーレ
ンス光源としてこの例では、スーパールミネツセ
ントダイオード（SLD）２０ａより発光された
光を、レンズ２０ｂを介して放射するようにして
構成している。"Example" An example of the present invention is shown in FIG. Components corresponding to those in the conventional example shown in FIG. 3 are given the same reference numerals, and redundant explanation will be omitted. The difference from FIG. 3 is that a low coherence light source 20 with a coherence length of several micrometers to several + micrometers is used as the light source, and an optical path length difference adjustment means 21 that can adjust the distance between the beam splitter 2 and the mirror 3 is provided. This is the point. In this example, such a low coherence light source is configured so that light emitted from a superluminescent diode (SLD) 20a is emitted through a lens 20b.
従来のレーザー光を用いる場合には、干渉性が
良いために、交叉領域における２つの照射光の光
路長に多少差があつても被測定体で散乱され、受
光された２つの散乱光は干渉し、受光素子９にお
いてヘテロダイン検波され、２つの散乱光の周波
数の差を持つ電気的信号を得ることができる。干
渉が起る光路長の差の最大値はコヒーレンス長と
呼ばれる。それ以上光路長に差があれば干渉は起
らない。レーザーではコヒーレンス長は比較的大
きく数百μm〜数ｍになる。従つて交叉領域７の
全域において２つの照射光の光路長の差がコヒー
レンス長以下となる。受光された２つの散乱光は
干渉し、受光素子９においてヘテロダイン検波さ
れて２つの散乱光の差を周波数が検出され、散乱
光のドツプラー周波数を測定することができる。
（このように散乱光相互の干渉の生ずる交叉領域
の全部又は一部を測定領域と呼ぶ。）
これに対して、この発明のようにコヒーレンス
長が数μm〜数＋μmの低コヒーレンス光源を用い
ると、コヒーレンス長が従来のレーザー光に比べ
て１桁或いはそれ以上小さくなる。このため、も
し交叉領域内に、２つの照射光の光路長が等しい
面が存在したとすれば、上述した測定領域２２
は、例えば第２図Ａ，Ｂに示すように、交叉領域
７内の光路長が等しい面の近傍の、コヒーレンス
長と対応するごく限られた領域となる。 When using conventional laser light, it has good coherence, so even if there is a slight difference in the optical path length of the two irradiated lights in the intersection area, it will be scattered by the object to be measured, and the two received scattered lights will interfere. Then, the light is heterodyne detected by the light receiving element 9, and an electrical signal having a difference in frequency between the two scattered lights can be obtained. The maximum value of the difference in optical path length at which interference occurs is called the coherence length. If the difference in optical path length is greater than that, no interference will occur. In a laser, the coherence length is relatively large, ranging from several hundred μm to several meters. Therefore, the difference between the optical path lengths of the two irradiated lights is equal to or less than the coherence length in the entire area of the intersection region 7. The two received scattered lights interfere, and are subjected to heterodyne detection in the light receiving element 9, and the frequency difference between the two scattered lights is detected, and the Doppler frequency of the scattered lights can be measured.
(All or part of the intersection region where mutual interference between scattered lights occurs is called a measurement region.) On the other hand, when a low coherence light source with a coherence length of several μm to several + μm is used as in the present invention, , the coherence length is one order of magnitude or more smaller than that of conventional laser light. Therefore, if there is a surface in the intersection area where the optical path lengths of the two irradiated lights are equal, the measurement area 22 described above
For example, as shown in FIGS. 2A and 2B, this is a very limited area corresponding to the coherence length near the plane with the same optical path length in the intersection region 7.
もし、交叉領域７内にこのような測定領域２２
が存在しない場合、或いは存在しても第２図Ａの
ようにその領域が大きい場合には、光路長差調整
手段２１によつて、２つの照射光の光路長差を調
整して、測定領域２２を、例えば第２図Ｂに示す
ように、片隅の小さな領域に設定することができ
る。光路長差調整手段２１は、第１図の実施例で
は、ミラー３及びレンズ５を移動台に収容して、
ビームスプリツター２とミラー３との間の距離を
可変できるような構成としている。 If there is such a measurement area 22 in the intersection area 7,
If the area does not exist, or even if it does exist, the area is large as shown in FIG. 22 can be set in a small area in one corner, for example as shown in FIG. 2B. In the embodiment shown in FIG. 1, the optical path length difference adjusting means 21 accommodates the mirror 3 and the lens 5 in a movable table.
The configuration is such that the distance between the beam splitter 2 and the mirror 3 can be varied.
コヒーレンス長が数μm以下の光源では測定領
域が小さ過ぎて、散乱光の安定な干渉が起り難
く、差の周波数の検出が困難となる。またコヒー
レンス長が数＋μm程度以上になると、測定領域
が大きくなつて、速度計の空間分解能が低下して
しまう。このような理由からこの発明ではコヒー
レンス長を前記の範囲に設定している。 For a light source with a coherence length of several μm or less, the measurement area is too small, making it difficult for stable interference of scattered light to occur, making it difficult to detect the frequency difference. Furthermore, when the coherence length exceeds several micrometers, the measurement area becomes large and the spatial resolution of the speedometer decreases. For this reason, in the present invention, the coherence length is set within the above range.
「発明の効果」
この発明によれば、従来のレーザーに代つて低
コヒーレンス光源が用いられると共に光路長差調
整手段が設けられているので、測定領域を交叉領
域内の片隅の小さな領域に設定することが可能と
なり、速度計の空間分解能を従来より大幅に向上
することができ、従つて被測定体の局所的な速度
分布も正確に測定することができる。"Effects of the Invention" According to the present invention, a low coherence light source is used in place of the conventional laser, and an optical path length difference adjustment means is provided, so that the measurement area can be set to a small area at one corner of the intersection area. This makes it possible to significantly improve the spatial resolution of the speedometer compared to the conventional method, and thus to accurately measure the local speed distribution of the object to be measured.
第１図はこの発明の光ドツプラー速度計の実施
例を示すブロツク系統図、第２図は第１図の実施
例の測定領域の説明に供するための拡大図、第３
図は従来の光ドツプラー速度計のブロツク系統
図、第４図は第３図の従来例の交叉領域の説明に
供するための拡大図、第５図は第３図の従来例に
おいて、ヘテロダイン検波して得られた信号の周
波数分布を示す図、第６図は第３図の従来例にお
いて送光用光フアイバー６，６′の尖端にそれぞ
れレンズ（図示せず）を設けて、交叉領域７を小
さく設定した場合の、ヘテロダイン検波された信
号の周波数分布を示す図である。
FIG. 1 is a block system diagram showing an embodiment of the optical Doppler velocimeter of the present invention, FIG. 2 is an enlarged view for explaining the measurement area of the embodiment of FIG. 1, and FIG.
The figure shows a block system diagram of a conventional optical Doppler velocimeter, Figure 4 is an enlarged view for explaining the crossover region of the conventional example in Figure 3, and Figure 5 shows heterodyne detection in the conventional example in Figure 3. FIG. 6 is a diagram showing the frequency distribution of the signal obtained by using the conventional example shown in FIG. FIG. 7 is a diagram showing the frequency distribution of a heterodyne detected signal when the frequency is set to a small value.
Claims (1)
周波数に差を与え、一方の光を被測定体の流れに
沿う方向より他方の光を被測定体の流れに逆う方
向より被測定体にそれぞれ照射し、それらの照射
光が互に交叉する交叉領域において、それぞれの
照射光が被測定体により散乱されて生じた散乱光
を受光し、それら散乱光の周波数の差を検出し、
それら散乱光のドツプラー周波数を測定して、上
記被測定体の速度を測定する光ドツプラー速度計
において、 上記光源としてコヒーレンス長が数μm乃至数
＋μm程度の低コヒーレンス光源を用いると共に、
上記２つの照射光の光路長に差を与えることがで
きる光路長調整手段を設けることを特徴とする光
ドツプラー速度計。[Claims] 1. Split the light from a light source into two, give a difference in the frequency of the split lights, and direct one light along the flow of the object to be measured, while the other light follows the flow of the object to be measured. The object to be measured is irradiated from opposite directions, and in the intersection area where the irradiated lights intersect with each other, the scattered light generated by each irradiated light being scattered by the object to be measured is received, and the frequency of the scattered light is detect the difference between
In an optical Doppler velocimeter that measures the speed of the object to be measured by measuring the Doppler frequency of the scattered light, a low coherence light source with a coherence length of several μm to several + μm is used as the light source, and
An optical Doppler velocimeter, characterized in that an optical Doppler velocimeter is provided with an optical path length adjusting means capable of giving a difference in the optical path length of the two irradiated lights.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23672786A JPS6390773A (en) | 1986-10-03 | 1986-10-03 | Optical doppler speed indicator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23672786A JPS6390773A (en) | 1986-10-03 | 1986-10-03 | Optical doppler speed indicator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6390773A JPS6390773A (en) | 1988-04-21 |
| JPH0447266B2 true JPH0447266B2 (en) | 1992-08-03 |
Family
ID=17004889
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23672786A Granted JPS6390773A (en) | 1986-10-03 | 1986-10-03 | Optical doppler speed indicator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6390773A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2447600A2 (en) | 2010-10-29 | 2012-05-02 | Stanley Electric Co., Ltd. | Lighting unit |
-
1986
- 1986-10-03 JP JP23672786A patent/JPS6390773A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2447600A2 (en) | 2010-10-29 | 2012-05-02 | Stanley Electric Co., Ltd. | Lighting unit |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6390773A (en) | 1988-04-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4540283A (en) | Apparatus and method for determining the size and velocity of particles, droplets, bubbles or the like using laser light scattering | |
| US4897536A (en) | Optical axis displacement sensor with cylindrical lens means | |
| US5394233A (en) | Apparatus for measuring high frequency vibration, motion, or displacement | |
| JPH0694596A (en) | Particle route determination device | |
| EP0947834B1 (en) | Detection of air flow speed and flow direction | |
| JP2755757B2 (en) | Measuring method of displacement and angle | |
| US3548655A (en) | Measurement of fluid or surface velocities | |
| US4997272A (en) | 4π laser Doppler anemometer (LDA) for measuring the velocities of moving objects | |
| US3680961A (en) | Measurement of particle sizes | |
| US4764014A (en) | Interferometric measuring methods for surfaces | |
| JPH0652170B2 (en) | Optical imaging type non-contact position measuring device | |
| Büttner et al. | Spatial resolving laser Doppler velocity profile sensor using slightly tilted fringe systems and phase evaluation | |
| JPH0447266B2 (en) | ||
| JPS60243583A (en) | Laser doppler speedometer | |
| GB2289814A (en) | Laser doppler velocimeter | |
| JPS6355035B2 (en) | ||
| EP0851210B1 (en) | Non-contact strain meter | |
| JPH07229913A (en) | Speedometer | |
| JPS63101702A (en) | Optical length measuring gauge | |
| JPH07167879A (en) | Laser doppler flow velocity meter | |
| JP3278508B2 (en) | Reference beam laser Doppler velocimeter | |
| JP2877119B2 (en) | Mobile body speed measurement device | |
| Merzkirch et al. | Measurement of shock wave velocity using the Doppler principle | |
| JPS5922907B2 (en) | Laser speed measuring device | |
| JP2924754B2 (en) | Optical differential velocity meter |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |