JP2004361291A - Droplet state measuring device and state measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously and accurately measure all elements of droplet particle diameters, three-dimensional distribution and three-dimensional speed distribution on the basis of a new measuring principle. <P>SOLUTION: A droplet state measuring device comprises a first camera 14 for capturing two obtained point-like light groups at each droplet respectively by irradiating each droplet in a region to be measured S with radiation sheet light LS (laser light), and a second camera 16 for capturing the point-like light group from an angle different from the first camera 14 in a focused focal point image. A droplet or a droplet group in the region to be measured S is identified on the basis of the focused focal point images captured with the first and second cameras 14 and 16 in a mode of a paired bright spot or a bright spot group constituted of the two obtained point-like light at each droplet. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００６８】
ここで、θはにらみ角、ｍは液滴の屈折率である。
【００６９】
実際にこの液滴の粒径を、（１）式から求めたところ１５３．５［μｍ］であった。
【００７０】
被測定領域Ａ内において同定された個々の液滴の粒径を測定した結果の分析例を図６に示す。図６では、被測定領域Ａ内の個々の液滴の粒径に対する液滴数のヒストグラムが示されている。この図６から、被測定領域Ａにおいては、液滴の直径が増加するとともに液滴数が減少することが分かる。最大液滴数は、液滴直径＝６０［μｍ］において記録されている。
【００７１】
同様な測定及び分析を被測定領域Ｂ以内の液滴についても行えば、被測定領域Ａ、Ｂ間の液滴の粒径に対する液滴数の違いが明確化される。
【００７２】
一方、被測定領域Ａ、Ｂ内において同定された個々の液滴は、本実施形態の構成上そのまま３次元の位置情報を内在している。この位置情報は、噴射口から噴霧された液滴の３次元分布（個々の液滴の３次元の位置情報）にほかならない。もちろん、得られた３次元分布の情報を、更にどのように分析するかは、もとより限定されるものではなく、さまざまな手法の分析が可能である。上記分析例もその一例と言える。
【００７３】
更に、第１、第２カメラ１４、１６によって撮影された映像を、所定の時間間隔で２セット以上入手した場合、各々の時点における各液滴の３次元空間における動きに関する情報を得ることができ、個々の液滴の移動軌跡を把握することができる。また、撮影の時間間隔と移動距離との関係から個々の液滴の３次元の速度分布を得ることもできる。
【００７４】
図７（ａ）に、被測定領域Ａにおける生の画像を、図７（ｂ）に速度分布に関する分析を行った後のパターン例をそれぞれ示す。この例では、被測定領域Ａにおいて複数個の液滴をまとめて同定し、当該複数個の液滴群に対応する輝点対群の速度分布を求めている。なお、ここでは、Ｘ−Ｙ方向の速度分布のみが示されており、Ｚ方向の速度分布は描かれていない。実際の測定ではＺ方向の速度分布は、カラーのレイヤー表示で表現される。
【００７５】
前述したように、本発明は、第１、第２カメラ１４、１６によって撮像された二枚の画像を基にして一個一個の液滴を個別に同定できるが、このように複数の液滴群をまとめて同定しても、相応の効果が得られる。どの程度の大きさの液滴群を纏めて捉えるかは、コスト、処理時間等を考慮して設定すればよい。
【００７６】
ところで、本発明では、被測定領域Ｓ内の各液滴を異なる角度から撮影した画像に基づいて同定する。そのため、撮影するカメラの台数を増やすことによって、様々な付加的な効果を得ることができるようになる。
【００７７】
図８に第１、第２カメラ１４、１６のほかに更に別のカメラを併設した実施形態の例を示す。図８の（ａ）においては、前記第１、第２のカメラ１４、１６のほかに、更に、センタカメラ（チェックカメラ）３０を備えた例が示されている。このセンタカメラ３０は、第１、第２のカメラ１４、１６のカメラ平面上において第１、第２カメラ１４、１６が放射シート光ＬＳに対して有しているそれぞれの角度の中間に相当する角度、すなわちステレオ角０度に相当する角度に設置されている。
【００７８】
この構成により、第１、第２のカメラに加え、センタカメラ３０によって捉えられた合焦点画像をも参照して、被測定領域Ｓ内の各小滴を輝点対の態様で同定できるようになる。その結果、各小滴の同定を一層誤りなく正確に行うことができるようになり、粒径測定も３次元空間における小滴の位置の把握もそれだけ正確に行うことができるようになる。
【００７９】
例えば粒径測定の場合に、第１、第２カメラ１４、１６によって特定の小滴が存在すると推定された空間に、センタカメラ３０も同一の輝点対画像をとらえていた場合に限り、その点状の２個の光点が確かに存在するある小滴の輝点対であるとして、粒径測定に利用できるようにソフトを構成すれば、誤って同定された輝点対をベースに粒径測定を行ってしまうのを防止できる。
【００８０】
このセンタカメラ３０は、当該センタカメラ３０によって撮像された合焦点画像を第１、第２のカメラによって撮像された合焦点画像と対等に扱い、３つのカメラによって得られた数値を平均化するような態様で利用してもよく、また、第１、第２カメラ１４、１６の相関に疑問が生じたときにのみ参照するような態様で利用してもよい。
【００８１】
また、前述したように、センタカメラ３０によって捉えられ合焦点画像は、ステレオ角０度における画像であるため、輝点対がより明確に捉えられている可能性が高いため、粒径測定に関しては、このセンタカメラ３０によって捉えられた輝点対をベースに測定するように構成してもよい。
【００８２】
一方、図８（ｂ）には、第１、第２のカメラ１４、１６のほかに、該第１、第２のカメラセットと同様の構成を有する第３、第４のカメラ２６、２８からなるカメラセットを同一のカメラ平面に併設するようにしている。この例では、同一のにらみ角θで、第１、第２カメラ１４、１６セットのステレオ角α１を小さめ（より零に近い値）に設定し、一方第３、第４カメラ２６、２８のセットのステレオ角α２を大きめ（より１８０°に近い値）に設定している。この結果、第１、第２カメラ１４、１６のセットによって、特に放射シート光ＬＳのシート面に平行な方向（Ｘ−Ｙ方向）において高い解像度を有する輝点対画像が得られ、第３、第４のカメラ２６、２８のセットによって放射シート光ＬＳの幅方向（Ｚ方向）において高い解像度を有する輝点対画像が得られる。この結果、一対のみのカメラセットを備える場合に比べ、３次元のあらゆる方向について、非常に高い精度で小滴の同定及び位置分布の確定が行えるようになる。
【００８３】
なお、このように、第３、第４のカメラセットを併設する場合、第１、第２のカメラセットの被測定領域と第３、第４のカメラセットの被測定領域が連続するように設置することも可能である。このように設置すると、動きの速い液滴でも１回の測定で画面から外れることなく連続して測定あるいは追跡できるようになる。
【００８４】
こうした３台以上のカメラによる連携測定の例は多々考えられる。追加するカメラの使用例は上記例に限定されない。
【００８５】
最後に、本発明を実際に実施する際に使用する具体的な装置の構成例について簡単に説明する。
【００８６】
図９は本状態計測装置１０の全体概略正面図、図１０はその斜視図、図１１はカメラ設置機構の全体概略図斜視図、図１２はその要部拡大斜視図である。なお、理解を容易にするために、これまで説明してきた部材と同様の機能を有する部材については、同一の符号をそのまま使用している。
【００８７】
この状態計測装置１０は、スワールノズルＮから噴霧される液滴の拡散状態を計測するためのもので、レーザ照射機構１２、第１カメラ１４、第２カメラ１６、及びコンピュータ（演算手段）１８ａ、１８ｂを主な構成要素として備える。
【００８８】
前記レーザ照射機構１２は、液滴が存在する３次元空間に対し、薄幅（厚さＷ）のシート状の放射シート光ＬＳを照射するもので、この実施形態では、ダブルパルスＮｄ：ＹＡＧレーザ（λ＝５３２ｎｍ、最大出力５０ｍＪ／パルス）が使用されている。
【００８９】
放射シート光ＬＳの厚さＷは、この実施形態では１ｍｍに設定されている。
【００９０】
図１１、図１２を参照して、第１、第２カメラ１４、１６設置するためのカメラ設置機構ＣＳは、レーザ照射機構１２ごと水平面内（Ｘ−Ｚ面内）で回転可能なターンテーブル３１上に配置されており、ベース体３２、Ｌ字アングル３４、および支持アーム３６、３７から主に構成される。ターンテーブル３１は、上下動も可能である。
【００９１】
ベース体３２は、放射シート光ＬＳが照射される方向（Ｘ方向）に沿ってターンテーブル３１上に固定されており、回転台４０の固定位置をＸ方向においてＭの範囲で可変とするための溝部４２を有する。
【００９２】
Ｌ字アングル３４はこの回転台４０上においてＸ−Ｚ平面内で回転してにらみ角θを調整・設定可能とする。また、Ｌ字アングル３４はこの回転台４０自体がベース体３２の溝部４２に沿って摺動可能とされていることにより、結果として被測定領域ＳをＸ方向に可変とする機能も有する。Ｌ字アングル３４の立柱３４Ａには、第１、第２カメラ１４、１６を支持するための支持アーム３６、３７がカメラ平面内で回転可能に取付けられている。支持アーム３６、３７は、これ自体が放射シート光ＬＳ（被測定領域Ｓ）に対して進退動自在とされており（または第１、第２カメラ１４、１６が支持アームに対して相対的に摺動可能とされており）、結果として第１、第２カメラ１４、１６の被測定領域Ｓに対する距離ｄ１、ｄ２が可変とされ、被測定対象の動き等を勘案して撮像可能空間の大きさを容易に変更することができるようになっている。
【００９３】
Ｌ字アングル３４及び支持アーム３６、３７の回転角は、それぞれエンコーダ４４、４５、４６によって検出され、現時点でのにらみ角θ及びステレオ角α（傾斜角α／２）が確認できるようになっている。また、必要ならば、この検出値に基づいて図示せぬリニヤモータを用いてにらみ角θ及びステレオ角αの自動設定を行うように構成することもできる。
【００９４】
図１１から明らかなように、この状態計測装置１０においては、光学系の配置関係をそのままに維持しながら、ターンテーブル３１を回転或いは上下動させることにより、カメラ支持機構ＣＳ全体をスワールノズルＮの中心軸（Ｙ軸）を基準にして３６０度回転させることができ、全方向の状態測定ができるようになっている。
【００９５】
なお、手動設定、あるいは自動設定のための初期設定の際には、図１３に示されるように、スワールノズルＮの装着ヘッド５０に取り付けた位置決めバー５２に、レーザポインタ５３を当て、指定された位置にマーカーが来るように画像を見ながら、被測定領域Ｓの調整を行う。
【００９６】
また、図１４に示されるように、回転台４０の回転・位置決めは、レーザ光源１２Ａからレーザポインタ５５を放ち、ノズル装着ヘッド５０に取り付け角度を調整したミラー５７を装着し、照度計５６により光度が最も高くなるように調整することにより行う。
【００９７】
なお、図９及び図１０において、符号７４は作業デスク、７６は試験流体供給機構をそれぞれ示している。試験流体供給機構７６は、流体を送り出すスクリュースピンドルポンプ８０、圧力を制御する水圧制御盤８２、試験流体回収タンク８４、配管８６等からなる。また、９０符号はレーザ光源１２Ａに信号を送るパルスジェネレータ、９２はレーザ光源１２Ａに付設されたシリンドリカルレンズをそれぞれ示している。また、符号９４は噴霧場の液滴の下方からの影響（巻き返し）の影響を抑制するためのハニカム整流ボードである。
【００９８】
第１、第２カメラ１４、１６は、１００８×１０１６ピクセルのＣＣＤカメラであり、焦点深さはこの例では１２．３ｍｍ、絞りはｆ＝１６である。これにより放射シート光ＬＳの厚さＷ内において両カメラが合焦点画像を記録するのに十分な被写界深度を得ている。
【００９９】
この実施形態ではこのにらみ角θは７０度に設定されている。可変範囲は５０度〜８０度である。実用上は６５度〜７５度程度がにらみ角θの最適範囲となることが多い。
【０１００】
また、ステレオ角αは、この例では５０度（水平線を境に上下２５度の傾斜）とされているが、２０度〜６０度（水平線を境に上下１０度〜３０度の傾斜）の範囲で可変である。
【０１０１】
以上の構成より、第１、第２カメラ１４、１６は、その被測定領域Ｓが放射シート光ＬＳ内の任意の位置に設定可能である。更に、液滴の存在する空間に対する放射シート光ＬＳの照射方向もターンテーブル３１の回転及び上下動により可変とされているため、液滴の存在する空間をトレースするようにして測定を繰り返すことにより、結果として液滴の存在する全範囲における３次元状態を液滴の粒径の測定を含めて実施できる。
【０１０２】
なお、第１、第２カメラ１４、１６のほかに別途のカメラを増設する場合においても、同様の構成の支持機構を採用することができる。
【０１０３】
尤も、本発明においては、第１、第２カメラ支持機構を含めて、具体的にどのような支持機構によって各カメラを支持・設置するかについては、特に限定されない。
【０１０４】
【発明の効果】
本発明によれば、３次元空間に存在する液滴や気泡等の小滴の粒径、３次元における分布状態、及び３次元における速度分布を同時にかつ正確に測定することができるようになるという優れた効果が得られる。
【図面の簡単な説明】
【図１】本発明の測定の基本原理を説明するための概念構成図
【図２】液滴の結像における光線軌跡の焦点面に対する関係を示す光学特性図
【図３】ノズルから噴出する噴霧の瞬間画像に被測定領域の表示を挿入した合成図
【図４】被測定領域Ｂの焦点面における噴霧を視覚化した画像および液滴の輝点対のサンプルを示す撮影図
【図５】ある輝点対およびその画像の自己相関関数のパターン図
【図６】被測定領域Ａ内において同定された個々の液滴粒径を測定した結果の分析例を示すヒストグラム
【図７】（ａ）は被測定領域Ｓａにおける生の撮影図、（ｂ）は速度分布に関する分析を行った後の速度パターン図
【図８】第１、第２カメラのほかに更に別のカメラを併設した実施形態の例を示す概略斜視図
【図９】本発明の実施形態に係る状態計測装置の具体的構成を示す全体概略正面図
【図１０】同斜視図
【図１１】カメラ設置機構の全体概略図斜視図
【図１２】同要部拡大斜視図
【図１３】位置決めバーを用いてカメラ設置機構により被測定領域の設定を行うときの説明図
【図１４】にらみ角を調整するときの具体的手法の例の説明図
【符号の説明】
１０…状態計測装置
１２…レーザ照射機構
１４…第１カメラ
１６…第２カメラ
１８ａ、１８ｂ…コンピュータ（演算手段）
２６…第３カメラ
２８…第４カメラ
３０…センタカメラ
ＬＳ…放射シート光
Ｗ…放射シート光の厚さ
Ｓ（Ａ、Ｂ）…被測定領域
θ…にらみ角
α…ステレオ角[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus and a method for measuring a state of a small droplet such as a droplet or a bubble existing in a three-dimensional space.
[0002]
[Prior art]
Devices for measuring the state of small droplets such as liquid droplets and bubbles existing in a three-dimensional space are required in many fields.
[0003]
For example, it is necessary to control the combustion state in order to reduce CO2 and Nox contained in exhaust gas discharged by combustion of an internal combustion engine. Proper evaluation of the distribution or diffusion state of the sprayed fuel greatly contributes to the development of a fuel injection nozzle for an internal combustion engine. In addition, distribution of small droplets existing in three-dimensional space, such as evaluation of spray characteristics of nebulizers, humidifiers, etc., measurement of distribution and diameter of steam rising from specific chemicals, etc., and observation of bubble behavior of beer and wine There is a great need for accurate measurement of diameter and diameter.
[0004]
Patent Document 1 (Japanese Patent Application Laid-Open No. 10-90157) discloses an example of a measuring apparatus using a laser diffraction method. The measurement principle of this device is that the laser emitting unit and its light receiving unit face the spray space, and the laser beam transmitted through the spray space is received by the light receiving unit to detect the scattering intensity distribution and transmittance in the spray space. Things. Generally, the scattering intensity distribution is adapted to a model of the particle size distribution of the spray, and the particle size distribution and the representative particle size of the spray are calculated. When the particle size distribution is calculated, the attenuation cross section of the particle group is calculated, and the average value of the volume concentration in the luminous flux is estimated from the measured transmittance.
[0005]
Conventionally, a method of specifying a position in a three-dimensional space and simultaneously measuring a plurality of particles by a method called LDV (laser Doppler flow velocity method), phase method LDV, PDPA (phase Doppler particle analysis method) or the like is proposed. Have been. The basic principle of this measurement method is that two laser beams are "crossed" in the air to form a spatial interference fringe, and the light scattered from a droplet traversing the interference fringe is observed at different points. The measurement volume is observed, and the diameter of the droplet is measured from the phase difference of the measurement signal.
[0006]
As a measuring method for obtaining a velocity field in a plane, PIV (particle image flow velocity measuring method) is known. This measurement method is based on the assumption that the arrangement pattern of droplets distributed in an observation area of a certain size does not change in the direction of flow for a certain period of time. By doing so, the movement distance is calculated. A three-dimensional SPIV (stereo particle image flow velocity measurement method) is also known.
[0007]
On the other hand, in recent years, a sheet-shaped parallel laser beam (radiation sheet light) is irradiated to the measurement space, and a small droplet hit by the laser beam is defocused due to interference between reflected light on the droplet surface and primary refracted light. A measurement method has been developed to analyze the interference fringes that occur in the image. This method, called laser interference imaging, involves the presence of interference fringes in the circular defocused image corresponding to each droplet, and a fixed relationship between the number of interference fringes and the diameter of the droplet. Focusing on a certain point, the diameter of the droplet can be measured with high accuracy by measuring the number of the interference fringes (Non-Patent Document 1: SAE Paper No. 950457, etc.).
[0008]
However, in this measurement method, since the out-of-focus image itself occupies a large area in a circular shape, if the distribution density of the droplets in the space is high, the out-of-focus images overlap with each other. There is a problem that it is difficult to measure the diameter.
[0009]
In this regard, in Patent Document 2 (Japanese Patent Application Laid-Open No. 2002-181515), by devising an optical system, interference between circular out-of-focus images corresponding to small droplets is suppressed, and the out-of-focus image is analyzed. A technology that facilitates the above is disclosed. This technique compresses the circular defocused image corresponding to each droplet in one direction and makes it a linear image only in the other direction, so that even if the distribution density of droplets in space is high, The out-of-focus images can be separated from each other, and the number of interference fringes in the out-of-focus images can be counted accurately.
[0010]
In addition, in this Patent Document 2, in addition to this, a method of obtaining the center position of the droplet by obtaining the center of the linear defocused image, or a method of Fourier transforming the linear defocused image to reduce the frequency A more specific method is to obtain the number of interference fringes in the out-of-focus image by multiplying the obtained frequency by the length of the out-of-focus image, and obtain the diameter of the droplet based on the number of the interference fringes. It is also disclosed. Further, two sets of two-dimensional frozen images are photographed at a minute interval, and the direction and distance in which the specific linear defocused image itself has moved between the two sets of two-dimensional frozen images are obtained by a cross-correlation calculation. A method is also disclosed.
[0011]
[Patent Document 1]
JP-A-10-90157
[Non-patent document 1]
SAE Paper No. 950457
[Patent Document 2]
JP-A-2002-181515
[0012]
[Problems to be solved by the invention]
However, the measuring method according to Patent Document 1 has a problem that although the distribution of the droplet diameter can be measured, information on the position of the droplet cannot be obtained. For this reason, it is not possible to obtain information on what trajectory or speed of the sprayed droplet spreads in space. In addition, since the laser transmitting unit and the light receiving unit are exposed in the spray space, there is a serious problem that the original flow of the spray is disturbed by the presence of the laser transmitting unit and the light receiving unit.
[0013]
Also, since the measuring method called the LDV, the phase method LDV, the PDPA or the like measures the diameter of a small droplet in an extremely narrow region where laser beams intersect (close to a point), a surrounding space outside the region is measured. It was difficult to measure the inside of the droplet at the same time, and it was difficult to understand the spatial relationship between the behavior of the droplets and to analyze the unsteady spray field such as turbulence. Also, the measurement accuracy was not always sufficient.
[0014]
On the other hand, the measuring method belonging to the category of the PIV can know the three-dimensional velocity distribution, but cannot measure the particle size of each droplet. In addition, since it is not originally focused on the behavior of the particle size of individual droplets, it is considered that when measuring a flow field in which individual particle velocities differ greatly, it is difficult to detect the movement amount of the particle group. . With respect to the particle size, an improved method that attempts to obtain the particle size from the brightness profile of the droplet image has been proposed, but only a rough particle size measurement result has been obtained. In addition, since the brightness profile increases in proportion to the square of the particle diameter, there is a possibility that the velocity and the particle diameter are obtained as velocity distribution of large-diameter particles in the measurement space or averaged information. high. The problem still remains that the dynamic range of the measurement is greatly reduced when the density of the droplets is high.
[0015]
The technique according to Patent Literature 2 (Japanese Patent Application Laid-Open No. 2002-181515) in which the laser interferometry is improved can accurately determine the particle diameter of each droplet by analyzing interference fringes generated in an out-of-focus image. However, although it is a technique that has been attracting attention in recent years, there is a major problem that positional information (distribution information) and velocity information of a droplet can be captured only in a two-dimensional observation field.
[0016]
Generally, when examining the particle size or distribution of droplets existing in a three-dimensional space, two-dimensional observation alone is not sufficient. In particular, the spatial concentration of dispersed droplets floating in a turbulent flow is not always uniform, and the density of the droplets may be uneven depending on the spatial structure of the flow field, and high or low concentration regions may occur locally. Are known. As a result, measurements based on this laser interferometry sometimes only show local high-density or low-density droplet distribution or velocity information that happened to be on a particular plane in space. It has been pointed out that the original distribution state or speed information may not always be reflected. However, it is impossible to reconstruct a three-dimensional distribution or speed from the obtained image information as long as a technique of obtaining interference fringes from an out-of-focus image is used.
[0017]
Even if an out-of-focus image is optically processed to be linearized and a method of separating overlapping droplet images is adopted, each individual droplet image is considered to be an image having a considerable length. The images are magnified and, depending on the density of the droplets, the images also overlap considerably. That is, as the droplet density increases, the resolution of the distribution must be relatively low.
[0018]
As described above, conventionally, a measurement method capable of accurately and simultaneously measuring the particle diameter, the three-dimensional distribution, and the three-dimensional velocity of small droplets such as droplets and bubbles existing in a three-dimensional space has not yet been developed. Therefore, in order to accurately measure all of these factors, it was a fact that separate measurements using different kinds of measurement methods had to be performed in parallel.
[0019]
The present invention has been made to drastically improve the situation concerning the state measurement of the conventional droplets, and it is possible to simultaneously and accurately measure all of these elements based on a new measurement principle. It is an object of the present invention to provide a droplet state measuring device and a state measuring method.
[0020]
[Means for Solving the Problems]
The present invention relates to a droplet state measuring device for measuring the state of a droplet such as a droplet or a bubble existing in a three-dimensional space. A laser irradiation mechanism capable of irradiating the radiation sheet light, and a point that two droplets are obtained for each droplet by irradiating each droplet present in an area to be measured in the radiation sheet light with the radiation sheet light. A first camera that captures a group of light beams in a focused image from outside the range irradiated with the radiation sheet light, and a group of point-like lights outside the range irradiated with the radiation sheet light. And a second camera that captures an in-focus image from a different angle from the first camera, wherein each of the point-like light groups captured by the first and second cameras is combined. Based on the focus image, a droplet or small droplet in the measured area The above problem is solved by configuring the group to be identifiable in a three-dimensional space in the form of a bright point pair or a bright point pair group composed of two point-like lights obtained for each droplet. It was done.
[0021]
FIG. 2 shows the relationship of the ray trajectory to the focal plane P1 when the parallel laser light LSo is irradiated on the small droplet P such as a droplet or a bubble. When the transparent spherical droplet P is irradiated with the parallel laser beam LSo, a double image of a bright spot (two points obtained on the focal plane) is generated on the focal plane due to the zero-order reflection and the first-order refraction (or the second-order refraction) of the droplet P. Light (bright point pair GP) is formed. In the figure, θ is a glare angle (scattering angle: described later). The bright spot pair GP has information on the particle size of the droplet P. However, when a large number of droplets actually present in the measurement space are imaged, the large number of bright spot pairs GP are scattered over the entire imaging surface in the state of a raw image, so that each small droplet is one by one. It is impossible to identify P (see FIGS. 4 and 7A).
[0022]
In the present invention, this bright point pair is captured as an in-focus image (rather than the technique of obtaining an interference fringe by imaging this bright point pair on an out-of-focus surface as in the technique according to Patent Document 2). At the same time, a method of “searching and identifying” each droplet by adopting a method in which each droplet is captured from different angles by the first and second cameras and each stereoscopic image (two images) is compared is adopted. . That is, in the present invention, a stereo image is used as a means for searching for and identifying each individual droplet itself.
[0023]
In the present invention, point-like lights scattered countlessly in a discrete state are identified under the concept of two paired point-like light points, that is, a “bright point pair”. Therefore, each droplet can be individually identified. In addition, since each of the identified small droplets is described in the form of a focused bright spot pair, the droplets inherently contain information on the particle size, and the information (regardless of the size of the particle size). Sr) Optically correctly reflects the particle size.
[0024]
Further, since the focused bright spot pair has almost no area, even if the droplets are densely present in the measured area, the drawing interference between the droplets hardly occurs. Therefore, depending on the resolution of the camera or the lens, even in a space in which small-diameter droplets that cannot be measured conventionally exist in high density, individual droplets can be reliably identified.
[0025]
In addition, the present invention is superior in that the two focused images captured from different angles by the first and second cameras not only contribute to the identification of individual droplets, but also That is, at the time of the identification, information on the three-dimensional distribution (the position in three dimensions) of each droplet in the measured area is also included at the same time. That is, the analysis relating to the bright spot pairs of the respective droplets present on the two image planes according to the present invention enables the three-dimensional distribution state of the respective droplets in the measured area to be simultaneously grasped.
[0026]
Further, in the present invention, since each individual droplet can be specified in the form of a bright point pair, the state at a specific time and the state after a lapse of a short time from the first and second cameras are respectively imaged. Thereby, it is possible to obtain the movement information of each droplet on each image plane captured by the first and second cameras. Therefore, it is also possible to calculate the three-dimensional movement trajectory and speed information of each small droplet by their mutual relationship.
[0027]
That is, according to the present invention, it is possible to simultaneously acquire the particle diameter of each droplet, the three-dimensional distribution (three-dimensional position information), the three-dimensional movement trajectory, and the three-dimensional velocity (three-dimensional vector information), which were conventionally impossible. is there.
[0028]
By the way, the present invention has the “possibility” of being able to identify all the droplets present in the measurement area in principle, and as a result, the particle size and the three-dimensional distribution ( (3D positional information), and further, 3D velocity distribution can be measured. However, the present invention does not necessarily require that all droplets present in the measurement area be identified in individual droplet units in the actual measurement, but merely identifies the number or mode according to the purpose. It may be enough.
[0029]
For example, when it is desired to determine the particle size, it is not necessary to identify all the droplets in the measurement area. In this case, the number of steps that need to be calculated and the number of steps for identification are limited. It suffices to measure the particle size only for the droplets identified under the conditions.
[0030]
Also, in the measurement of the three-dimensional distribution or the three-dimensional velocity distribution, when it is difficult to identify all the droplets due to the resolution of the first and second cameras or the processing capability of the computer. For example, a group of bright spot pairs formed by a plurality of droplet groups may be searched and identified as one lump. Even in this case, the plurality of droplet groups can be identified as a group-level droplet group which is assumed to have the same three-dimensional position and perform the same behavior (that is, the original position is different but the two-dimensional information is different). (It is not considered that they happen to be at the same position because they were viewed as), and the reliability of the position information and the behavior tracking information is high. Therefore, even when an image is obtained after a lapse of a predetermined time in order to obtain speed information, tracking is easy, and sufficient information can be obtained depending on the application.
[0031]
Whether to identify a single droplet or a plurality of droplets is to be selected mainly in relation to the resolution of the camera, the computing power of the computer, or the processing time and cost. In this respect, it is possible to flexibly cope with the purpose.
[0032]
In the present invention, there is a “possibility” that can simultaneously measure any of the droplet diameter, the three-dimensional distribution, the three-dimensional movement trajectory, the three-dimensional velocity, and the like. Needless to say, it is not always necessary to perform all of these measurements at the same time, and only one of the measurement items may be calculated according to the purpose, and unnecessary calculation may be omitted.
[0033]
Various variations are conceivable for the present invention.
[0034]
For example, as the two dot-like lights obtained by irradiating the droplets with the radiation sheet light, the 0-order reflected light and the primary refracted light of the droplet are selected, so that each droplet is bright and clear. Luminescent spot pairs can be obtained. In other words, the present invention can also select, for example, the secondary refracted light of a droplet as an object forming a bright spot pair.
[0035]
When measuring the diameter of the droplet, the interval between the bright spot pairs may be calculated by an autocorrelation method. The method of calculating the distance between two points by the autocorrelation method itself is known. This calculation has a lighter calculation load than a method of analyzing interference fringes using Fourier transform, for example.
[0036]
Further, when the depth (thickness) of the radiation sheet light in the width direction is variable, it is possible to obtain a measurement area having a size that matches the measurement purpose. That is, when the depth of the radiation sheet light in the width direction is deep (thick), the depth of the three-dimensional space that can be measured can be increased. Large droplets can be reliably tracked. On the other hand, when the existence density of droplets is high, the number of droplets to be imaged (the number of pairs of bright spots) increases, which not only increases the load of arithmetic processing for identifying each bright spot pair, but also increases The probability that identification will be performed will increase accordingly. In such a case, if the depth of the radiation sheet light in the width direction is reduced, the number of imaged bright spot pairs can be reduced. If the depth in the width direction of the radiation sheet light is variable, such adjustment according to the purpose can be easily performed.
[0037]
The first and second cameras may be arranged so that their respective optical axes intersect with the sheet plane of the radiation sheet light at an intersection angle other than a right angle (glare angle and stereo angle: detailed later).
[0038]
In general, the 0-order reflected light, the first-order refracted light, or the second-order refracted light has different luminances. If the first and second cameras are arranged with a “glare angle” such that the optical axis of the camera intersects the sheet plane of the radiation sheet light at an angle other than a right angle, the difference can be reduced. As a result, the identification of the droplet can be performed more reliably.
[0039]
In this case, if the glare angle is variable, the camera arrangement is easily adjusted to obtain the clearest bright spot pair according to the characteristics of the measured object, such as the transparency and the refractive index. And the degree of freedom of setting can be increased.
[0040]
If the angle (stereo angle) between the optical axes of the first and second cameras is variable, the resolution and the depth (width) of the measured area in the three-dimensional space in the direction of the radiation sheet surface. It is possible to easily adjust the resolution in the direction.
[0041]
In addition, when the distance between the first and second cameras with respect to the measurement area is variable, the size of the imageable space can be easily changed in consideration of the movement of the measurement object and the like. Become.
[0042]
Further, if the measured area imaged by the first and second cameras can be set at an arbitrary position in the space where the small droplet exists, by tracing the measured area, the existence of the small droplet can be determined. Measurement of the entire three-dimensional space can be performed.
[0043]
By the way, in the present invention, the basic configuration is to identify each droplet in the measured area based on the in-focus images captured by the first and second cameras, respectively. The installation of a camera other than the two cameras is not prohibited, and another camera may be provided as appropriate according to the application or purpose.
[0044]
For example, in addition to the first and second cameras, the point-like light group is further outside the range irradiated with the radiation sheet light and is different from any of the first and second cameras. A check camera that captures an in-focus image from an angle is provided. In addition to the first and second cameras, a reference is made to the in-focus image captured by the check camera, and a droplet (or droplet group) in the measurement area is referred to. ) Can be identified so that each droplet can be more accurately identified, and the position of the droplet in the three-dimensional space can be grasped more accurately. Become.
[0045]
Note that this check camera treats the focused image captured by the check camera as equal to the focused image captured by the first and second cameras, and averages the numerical values obtained by the three cameras. It may be used in such a manner that it is referred to only when a question arises in the correlation between the first and second cameras.
[0046]
This check camera has its own optical axis in a camera plane including the optical axes of the first and second cameras, and is installed at a position corresponding to the center of the first and second cameras. It is even better. In general, when focusing only on the function of clearly capturing a bright point pair, it is most preferable to install a camera at a position corresponding to a stereo angle of 0 degree with respect to the radiation sheet light. Therefore, if a focused image of a small droplet at a stereo angle of 0 degree is separately present, not only can the probability of erroneous identification being reduced be reduced, but also because the bright spot pair is clearly captured, for example, to determine the interval thereof In the calculation by the autocorrelation method, the peak can be easily found, so that the droplet diameter of the droplet can be calculated more accurately in some cases.
[0047]
Further, in addition to the first and second cameras, one or two or more camera sets having the same configuration as the first and second camera sets may be provided. For example, when a set of first and second cameras having the same glancing angle and a small stereo angle and a set of the third and fourth cameras having a large stereo angle are combined, the set of the first and second cameras can be used as follows. In particular, a bright point pair image having a high resolution in the direction parallel to the sheet surface of the radiation sheet light is obtained, and a bright point pair image having a high resolution in the width direction of the radiation sheet light is obtained by the third and fourth sets of cameras. can get. As a result, the identification of the droplet and the determination of the position distribution can be performed with extremely high accuracy in all three-dimensional directions as compared with the case where only a pair of camera sets are provided.
[0048]
In addition, for example, if the measurement area of the first and second camera sets and the measurement area of the third and fourth camera sets are set to be continuous, a wide range of droplets can be measured in one measurement. The distribution or movement can be continuously measured or tracked in a highly accurate focused state.
[0049]
Such linked measurement by three or more cameras can be assumed as an advanced form of the present invention because the present invention performs the identification analysis based on the focused image of the bright spot pair. It can be said that it shows the target possibility.
[0050]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0051]
FIG. 1 is a conceptual configuration diagram for explaining the basic principle of measurement according to the present invention.
[0052]
The measurement target in this embodiment is a droplet (small droplet) sprayed downward from the swirl nozzle N. For convenience, the horizontal direction in which the radiation sheet light LS is emitted is the X direction, the vertical direction (the direction in which the central axis of the swirl nozzle N extends) is the Y direction, and the horizontal direction (radiation) is perpendicular to both the X and Y directions. The width direction of the sheet light LS) is defined as a Z direction. The origin of each direction is the injection port of the swirl nozzle N.
[0053]
With reference to FIG. 1, a state measurement device 10 includes a laser irradiation mechanism 12, a first camera 14, a second camera 16, and a computer (arithmetic unit: not shown) as main components.
[0054]
The laser irradiation mechanism 12 irradiates the light-emitting sheet light LS having a thin width (thickness W) from the light source 12A to the three-dimensional space where the liquid droplet exists, and is itself known. .
[0055]
The radiation sheet light LS is a fan-shaped light that expands vertically symmetrically in a vertical plane (within the XY plane) around a horizontal line x0 in the X direction with the light source 12A of the laser irradiation mechanism 12 as a base point. The thickness W of the radiation sheet light LS in the Z direction becomes the substantial depth in the Z direction of the measured area S in this embodiment. That is, when the thickness W is set to be large, the depth of the measured area S in the Z direction can be increased. Conversely, when the thickness W is set to be small, the number of droplets irradiated with the radiation sheet light LS decreases, so that it is possible to obtain an image with little interference between droplets (easy to identify). Therefore, qualitatively, when the movement of the droplet is large, the thickness W is increased to secure a deep area to be measured S, and when the existence density of the droplet is high, the thickness W of the radiation sheet light LS is increased. If the number of droplets to be imaged is suppressed by making the value smaller, a more desirable measurement result can be obtained.
[0056]
Note that the boundaries in the X direction and the Y direction of the measured area S are determined as overlapping portions of the respective imaging areas of the first and second cameras.
[0057]
When the radiation sheet light is applied to each droplet existing in the measurement target area S, as described above, two dot-like lights (0-order reflection light and primary refraction light) are provided for each droplet, respectively. (A bright spot pair) is obtained (see FIG. 2).
[0058]
The first camera 14 emits the emission sheet light LS so that a group of bright spot pairs obtained for each droplet by irradiating the emission sheet light LS to each droplet can be captured in a focused image. It is located outside the range that is being irradiated. On the other hand, the second camera 16 is arranged so as to capture the same group of the luminescent spot pairs as a focused image from an angle different from that of the first camera and outside the range in which the radiation sheet light LS is irradiated. The two cameras 14, 16 are CCD cameras, and are arranged in a so-called stereo PIV arrangement.
[0059]
More specifically, the optical axes 14A and 16A of the first and second cameras 14 and 16 respectively intersect with the sheet plane of the radiation sheet light LS at an angle θ other than a right angle in the XZ plane. I have. This intersection angle θ is herein referred to as “glare angle”. The glare angle θ is set to an angle other than 90 degrees in order to reduce the difference in luminance between the 0-order reflected light and the primary refracted light as much as possible so that both have substantially the same luminance. The glare angle θ is desirably variable because the optimum value differs depending on the characteristics of the droplet such as transparency and refractive index.
[0060]
The angle α between the optical axes 14A, 16A of the first and second cameras 14, 16 is also variable. This angle α is referred to herein as a “stereo angle”. The setting of the stereo angle α (more specifically, the setting of the inclination angle α / 2 from the horizontal plane corresponding to そ の thereof) is related to the identification of the droplet in the three-dimensional space of the measurement target area S, and the radiation sheet light This affects the adjustment of the resolution of the LS in the sheet surface direction (X-Y direction) and the resolution in the depth direction (Z direction). When the stereo angle α is set small, the resolution in the sheet surface direction can be increased, and when the stereo angle α is set large, the resolution in the depth direction (Z direction) can be increased.
[0061]
The distances d1 and d2 (d1 = d2) of the first and second cameras 14 and 16 with respect to the measurement area S are also variable. This is to make it possible to easily change the size of the imageable space in consideration of the movement of the object to be measured.
[0062]
Note that the camera plane including the optical axes 14A and 16A of the first and second cameras 14 and 16 is a coordinate axis (a coordinate axis in the Y direction in this embodiment) corresponding to the direction in which the radiation sheet light LS is spreading. Parallel. The first and second cameras 14 and 16 are symmetrically opposed to the radiation sheet light LS, and have the same glancing angle θ and the same inclination angle from the horizontal plane (corresponding to １ ／ of the stereo angle α). , And the distances d1 and d2 to the measured area S are also the same.
[0063]
With the above configuration, the measurement target area S of each of the first and second cameras 14 and 16 can be set at an arbitrary position in the radiation sheet light LS. Therefore, for example, the irradiation direction itself of the radiation sheet light LS with respect to the space where the droplet is present is made variable as described later, and the measurement is repeated so as to trace the measurement target area S. The state of the droplet can be measured in all three-dimensional spaces.
[0064]
FIG. 3 shows an example of the instantaneous image of the spray ejected from the nozzle and the measured area S (A, B). The centers of the measured areas A and B are located at positions of 20 mm in the X direction, 50 mm in the Y direction, 35 mm in the X direction, and 70 mm in the Y direction, respectively, as viewed from the center of the injection port Na of the swirl nozzle N.
[0065]
FIGS. 4A and 4B show an image in which the spray on the focal plane of the measurement area B is visualized and a sample of the bright spot pair of the droplet. These images are recorded by the first and second cameras 14 and 16 which have a three-dimensional structure with respect to the area B to be measured.
[0066]
FIGS. 5A and 5B show a certain bright spot pair and an autocorrelation function pattern of the image. The interval between the 0th-order peak and the 1st-order peak of the correlation value corresponds to the interval L between the bright spot pairs. Knowing the distance between the luminescent spot pairs, the particle diameter of the droplet can be calculated based on the known equation (1).
[0067]
(Equation 1)

[0068]
Here, θ is the glancing angle, and m is the refractive index of the droplet.
[0069]
When the particle diameter of the droplet was actually calculated from the equation (1), it was 153.5 [μm].
[0070]
FIG. 6 shows an analysis example of the result of measuring the particle size of each droplet identified in the measurement target area A. FIG. 6 shows a histogram of the number of droplets with respect to the particle size of each droplet in the measurement target area A. From FIG. 6, it can be seen that in the measurement target area A, the diameter of the droplet increases and the number of droplets decreases. The maximum number of droplets is recorded at a droplet diameter of 60 [μm].
[0071]
If the same measurement and analysis are performed on the droplets within the measurement region B, the difference in the number of droplets with respect to the droplet diameter between the measurement regions A and B is clarified.
[0072]
On the other hand, each of the droplets identified in the measurement areas A and B has three-dimensional position information as it is in the configuration of the present embodiment. This position information is nothing less than the three-dimensional distribution of the droplets sprayed from the ejection port (the three-dimensional position information of each droplet). Of course, how to further analyze the obtained three-dimensional distribution information is not limited to a particular one, and various methods can be analyzed. The above analysis example can be said as one example.
[0073]
Further, when two or more sets of images captured by the first and second cameras 14 and 16 are obtained at predetermined time intervals, information on the movement of each droplet in the three-dimensional space at each time can be obtained. In addition, the movement trajectory of each droplet can be grasped. In addition, a three-dimensional velocity distribution of each droplet can be obtained from the relationship between the imaging time interval and the moving distance.
[0074]
FIG. 7A shows a raw image in the measurement target area A, and FIG. 7B shows an example of a pattern after the velocity distribution is analyzed. In this example, a plurality of droplets are collectively identified in the measurement target area A, and a velocity distribution of a bright spot pair group corresponding to the plurality of droplet groups is obtained. Here, only the velocity distribution in the X-Y direction is shown, and the velocity distribution in the Z direction is not drawn. In the actual measurement, the velocity distribution in the Z direction is represented by a color layer display.
[0075]
As described above, according to the present invention, each droplet can be individually identified based on two images captured by the first and second cameras 14 and 16. Even if they are identified collectively, a corresponding effect can be obtained. The size of the droplet group to be collectively captured may be set in consideration of cost, processing time, and the like.
[0076]
In the present invention, each droplet in the measurement target area S is identified based on images captured from different angles. Therefore, various additional effects can be obtained by increasing the number of cameras that shoot images.
[0077]
FIG. 8 shows an example of an embodiment in which another camera is provided in addition to the first and second cameras 14 and 16. FIG. 8A shows an example in which a center camera (check camera) 30 is provided in addition to the first and second cameras 14 and 16. The center camera 30 corresponds to the middle of the respective angles of the first and second cameras 14 and 16 with respect to the radiation sheet light LS on the camera plane of the first and second cameras 14 and 16. It is installed at an angle, that is, an angle corresponding to a stereo angle of 0 degree.
[0078]
With this configuration, each droplet in the measured area S can be identified in the form of a bright point pair with reference to the in-focus image captured by the center camera 30 in addition to the first and second cameras. Become. As a result, the identification of each droplet can be performed more accurately and without error, and the particle size measurement and the grasp of the position of the droplet in the three-dimensional space can be more accurately performed.
[0079]
For example, in the case of particle size measurement, only when the center camera 30 also captures the same bright spot pair image in the space where the specific droplet is estimated to be present by the first and second cameras 14 and 16, If the software is configured so that it can be used for particle size measurement assuming that two dot-like light spots are indeed the bright spot pair of a certain droplet, the particle is based on the erroneously identified bright spot pair. Diameter measurement can be prevented.
[0080]
The center camera 30 treats the focused image captured by the center camera 30 equally with the focused images captured by the first and second cameras, and averages the numerical values obtained by the three cameras. The first and second cameras 14 and 16 may be used only when there is a question.
[0081]
In addition, as described above, the focused image captured by the center camera 30 is an image at a stereo angle of 0 degrees, and thus it is highly possible that a bright spot pair is more clearly captured. Alternatively, the measurement may be performed based on the bright spot pairs captured by the center camera 30.
[0082]
On the other hand, in FIG. 8B, in addition to the first and second cameras 14 and 16, third and fourth cameras 26 and 28 having the same configuration as the first and second camera sets are shown. Camera sets are arranged on the same camera plane. In this example, with the same glancing angle θ, the stereo angle α1 of the first and second cameras 14 and 16 is set smaller (a value closer to zero), while the set of the third and fourth cameras 26 and 28 is set. Is set to a relatively large value (a value closer to 180 °). As a result, with the set of the first and second cameras 14 and 16, a bright spot pair image having a high resolution is obtained, especially in a direction (XY direction) parallel to the sheet surface of the radiation sheet light LS. With the set of the fourth cameras 26 and 28, a bright spot pair image having high resolution in the width direction (Z direction) of the radiation sheet light LS is obtained. As a result, the identification of the droplet and the determination of the position distribution can be performed with extremely high accuracy in all three-dimensional directions as compared with the case where only a pair of camera sets are provided.
[0083]
In the case where the third and fourth camera sets are installed side by side, the measurement areas of the first and second camera sets and the measurement areas of the third and fourth camera sets are connected so as to be continuous. It is also possible. With this arrangement, even a fast-moving droplet can be continuously measured or tracked without going off the screen in one measurement.
[0084]
Many examples of such cooperative measurement with three or more cameras are conceivable. The usage example of the camera to be added is not limited to the above example.
[0085]
Finally, a brief description will be given of an example of the configuration of a specific device used when actually implementing the present invention.
[0086]
9 is an overall schematic front view of the present state measuring device 10, FIG. 10 is a perspective view thereof, FIG. 11 is an overall schematic perspective view of a camera installation mechanism, and FIG. For easy understanding, the same reference numerals are used for members having the same functions as those described above.
[0087]
This state measuring device 10 is for measuring the diffusion state of droplets sprayed from the swirl nozzle N, and includes a laser irradiation mechanism 12, a first camera 14, a second camera 16, and a computer (arithmetic means) 18a, 18b as a main component.
[0088]
The laser irradiation mechanism 12 irradiates a thin radiation sheet light LS having a thin width (thickness W) to a three-dimensional space where a droplet exists. In this embodiment, a double pulse Nd: YAG laser is used. (Λ = 532 nm, maximum output 50 mJ / pulse).
[0089]
The thickness W of the radiation sheet light LS is set to 1 mm in this embodiment.
[0090]
Referring to FIGS. 11 and 12, a camera installation mechanism CS for installing the first and second cameras 14 and 16 includes a turntable 31 rotatable in a horizontal plane (in the XZ plane) together with the laser irradiation mechanism 12. It is disposed on the upper side and mainly includes a base body 32, an L-shaped angle 34, and support arms 36 and 37. The turntable 31 can also move up and down.
[0091]
The base body 32 is fixed on the turntable 31 along the direction in which the radiation sheet light LS is irradiated (X direction), and is used to change the fixed position of the turntable 40 in the X direction within a range of M. It has a groove 42.
[0092]
The L-shaped angle 34 rotates on the turntable 40 in the XZ plane so that the glare angle θ can be adjusted and set. The L-shaped angle 34 also has a function of making the measured area S variable in the X direction as a result of the turntable 40 itself being slidable along the groove 42 of the base body 32. Support arms 36 and 37 for supporting the first and second cameras 14 and 16 are attached to the uprights 34A of the L-angle 34 so as to be rotatable in the plane of the camera. The support arms 36 and 37 are capable of moving forward and backward with respect to the radiation sheet light LS (measurement area S) (or the first and second cameras 14 and 16 are relatively movable with respect to the support arm). As a result, the distances d1 and d2 of the first and second cameras 14 and 16 with respect to the measurement area S are made variable, and the size of the imageable space in consideration of the movement of the measurement target and the like. It can be easily changed.
[0093]
The rotation angles of the L-shaped angle 34 and the support arms 36 and 37 are detected by encoders 44, 45 and 46, respectively, so that the glare angle θ and the stereo angle α (tilt angle α / 2) at the present time can be confirmed. I have. Further, if necessary, a configuration may be employed in which the glare angle θ and the stereo angle α are automatically set using a linear motor (not shown) based on the detected values.
[0094]
As is clear from FIG. 11, in the state measuring device 10, the entire camera support mechanism CS is moved by rotating or turning the turntable 31 while maintaining the arrangement relationship of the optical system. It can be rotated 360 degrees with respect to the central axis (Y axis), and can measure the state in all directions.
[0095]
At the time of initial setting for manual setting or automatic setting, as shown in FIG. 13, a laser pointer 53 is applied to a positioning bar 52 attached to the mounting head 50 of the swirl nozzle N, and the designated position is designated. The measurement area S is adjusted while looking at the image so that the marker comes to the position.
[0096]
Further, as shown in FIG. 14, the rotation and positioning of the turntable 40 are performed by emitting a laser pointer 55 from the laser light source 12A, mounting a mirror 57 having an adjusted mounting angle on the nozzle mounting head 50, and illuminance meter 56 Is adjusted to be highest.
[0097]
9 and 10, reference numeral 74 denotes a work desk, and 76 denotes a test fluid supply mechanism. The test fluid supply mechanism 76 includes a screw spindle pump 80 for sending out fluid, a hydraulic pressure control panel 82 for controlling pressure, a test fluid recovery tank 84, a pipe 86, and the like. Reference numeral 90 denotes a pulse generator for sending a signal to the laser light source 12A, and reference numeral 92 denotes a cylindrical lens attached to the laser light source 12A. Reference numeral 94 denotes a honeycomb rectifying board for suppressing the influence (rewinding) of the droplet in the spray field from below.
[0098]
The first and second cameras 14 and 16 are CCD cameras of 1008 × 1016 pixels, the depth of focus is 12.3 mm in this example, and the aperture is f = 16. As a result, the depth of field is sufficient for both cameras to record a focused image within the thickness W of the radiation sheet light LS.
[0099]
In this embodiment, the glare angle θ is set to 70 degrees. The variable range is 50 degrees to 80 degrees. In practice, about 65 to 75 degrees is often the optimal range of the glare angle θ.
[0100]
In this example, the stereo angle α is set to 50 degrees (inclination of 25 degrees vertically with respect to the horizontal line), but in a range of 20 degrees to 60 degrees (inclination of 10 degrees to 30 degrees with respect to the horizontal line) Is variable.
[0101]
With the above configuration, the measurement target area S of each of the first and second cameras 14 and 16 can be set at an arbitrary position in the radiation sheet light LS. Furthermore, since the irradiation direction of the radiation sheet light LS with respect to the space where the droplet is present is also variable by the rotation and vertical movement of the turntable 31, the measurement is repeated by tracing the space where the droplet is present. As a result, the three-dimensional state in the entire range where the droplet exists can be implemented, including the measurement of the particle size of the droplet.
[0102]
It should be noted that a support mechanism having the same configuration can be employed when an additional camera is added in addition to the first and second cameras 14 and 16.
[0103]
However, in the present invention, there is no particular limitation on what kind of support mechanism, including the first and second camera support mechanisms, specifically supports and installs each camera.
[0104]
【The invention's effect】
According to the present invention, it is possible to simultaneously and accurately measure the particle size of a small droplet such as a droplet or a bubble existing in a three-dimensional space, a three-dimensional distribution state, and a three-dimensional velocity distribution. Excellent effects can be obtained.
[Brief description of the drawings]
FIG. 1 is a conceptual configuration diagram for explaining a basic principle of measurement according to the present invention.
FIG. 2 is an optical characteristic diagram showing a relationship between a ray trajectory and a focal plane in image formation of a droplet.
FIG. 3 is a composite diagram in which a display of a measurement target region is inserted into an instantaneous image of a spray ejected from a nozzle.
FIG. 4 is a photograph showing an image visualizing the spray on a focal plane of a measurement area B and a sample of a bright spot pair of a droplet.
FIG. 5 is a pattern diagram of a certain bright spot pair and an autocorrelation function of the image.
FIG. 6 is a histogram showing an analysis example of the result of measuring the particle diameter of each droplet identified in the measurement area A;
7A is a raw photographed image in a measurement target area Sa, and FIG. 7B is a speed pattern diagram after an analysis on a speed distribution is performed;
FIG. 8 is a schematic perspective view showing an example of an embodiment in which another camera is provided in addition to the first and second cameras.
FIG. 9 is an overall schematic front view showing a specific configuration of the state measuring device according to the embodiment of the present invention.
FIG. 10 is a perspective view of the same.
FIG. 11 is a schematic perspective view of the entire camera installation mechanism.
FIG. 12 is an enlarged perspective view of the main part.
FIG. 13 is an explanatory diagram when a measurement target area is set by a camera installation mechanism using a positioning bar.
FIG. 14 is an explanatory diagram of an example of a specific method for adjusting a glare angle;
[Explanation of symbols]
10. State measurement device
12 ... Laser irradiation mechanism
14 ... First camera
16 Second camera
18a, 18b ... computer (arithmetic means)
26: Third camera
28: Fourth camera
30 ... Center camera
LS: radiation sheet light
W: Thickness of radiation sheet light
S (A, B) ... area to be measured
θ ... glancing angle
α ... Stereo angle

Claims (14)

In a droplet state measuring device for measuring the state of a droplet such as a droplet or a bubble existing in a three-dimensional space,
A laser irradiation mechanism capable of irradiating a thin sheet-shaped radiation sheet light to a space where a droplet to be measured exists;
The radiation sheet light irradiates a group of two point-like lights obtained for each of the droplets by irradiating the radiation sheet light to each droplet present in the measurement area in the radiation sheet light. A first camera that captures in-focus images from outside the range
A second camera that captures the group of point-like lights in a focused image outside a range where the radiation sheet light is irradiated and from a different angle from the first camera,
On the basis of the respective focused images of the point-like light groups captured by the first and second cameras, the droplets or droplet groups in the measurement target area are divided by 2 for each droplet. An apparatus for measuring the state of a small droplet, characterized in that it can be identified in a three-dimensional space in the form of a bright spot pair or a bright spot pair group composed of obtained point lights. In claim 1,
2. An apparatus for measuring the state of a droplet, wherein two or more sets of images of a group of point lights obtained by the first and second cameras can be acquired at predetermined time intervals. In claim 1 or 2,
A droplet state measuring device, wherein 0-order reflected light and primary refraction light of the droplet are selected as two point-like lights obtained by irradiating the radiation sheet light to the droplet. . In any one of claims 1 to 3,
An apparatus for measuring a state of a droplet, wherein a diameter of the droplet is measured by analyzing an interval between the bright spot pairs by an autocorrelation method. In any one of claims 1 to 4,
An apparatus for measuring a state of a droplet, wherein a depth of the radiation sheet light in a width direction is variable. In any one of claims 1 to 5,
An optical axis of each of the first and second cameras intersects the sheet plane of the radiation sheet light at an angle other than a right angle. In claim 6,
The state measuring device for small droplets, wherein an intersection angle between each optical axis of the first and second cameras and a sheet plane of the radiation sheet light is variable. In any one of claims 1 to 7,
An apparatus for measuring a state of a droplet, wherein an angle between optical axes of the first and second cameras is variable. In any one of claims 1 to 8,
A distance measuring apparatus for measuring the state of a droplet, wherein a distance between the first and second cameras with respect to the area to be measured is variable. In any one of claims 1 to 9,
The state measurement apparatus for a droplet, wherein the measurement area captured by the first and second cameras can be set at an arbitrary position in a space where the droplet is present. In any one of claims 1 to 10,
In addition to the first and second cameras, the group of point-like lights is further out of the range in which the radiation sheet light is irradiated and different from any of the first and second cameras. Equipped with a check camera that captures a focused image from an angle,
In addition to the first and second cameras, a droplet or a group of droplets in the measured area can be identified in a three-dimensional space with reference to a focused image captured by the check camera. A droplet state measuring device characterized by the following. In claim 11,
The check camera has its own optical axis in a camera plane including the optical axes of the first and second cameras, and is installed at a position corresponding to the center of the first and second cameras. Characteristic measuring device for droplets. In any one of claims 1 to 12,
An apparatus for measuring the state of a droplet, comprising at least a pair of camera sets having the same configuration as the first and second cameras, in addition to the first and second cameras. In a droplet state measurement method for measuring the state of a droplet such as a droplet or a bubble existing in a three-dimensional space,
Irradiating a thin sheet-shaped radiation sheet light with a laser irradiation mechanism to a space where a droplet to be measured exists, and
By irradiating the radiation sheet light to each droplet present in the measured area in the radiation sheet light, a group of two point-like lights obtained for each droplet is obtained for the radiation sheet light. Simultaneously capturing as two in-focus images visualized from different angles
On the basis of the two focused images, each of the small droplets or small droplet groups in the measured area is formed into a pair of luminescent spots or luminescent spots composed of two point-like lights obtained for each of the small droplets. Identifying in a pairwise manner;
A method for measuring the state of a droplet, comprising:

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