JPH02231673A - Evaluating method for correlation function - Google Patents
Evaluating method for correlation functionInfo
- Publication number
- JPH02231673A JPH02231673A JP1051953A JP5195389A JPH02231673A JP H02231673 A JPH02231673 A JP H02231673A JP 1051953 A JP1051953 A JP 1051953A JP 5195389 A JP5195389 A JP 5195389A JP H02231673 A JPH02231673 A JP H02231673A
- Authority
- JP
- Japan
- Prior art keywords
- correlation function
- value
- fluctuation
- correlation
- coefficient
- 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.)
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Links
- 238000005314 correlation function Methods 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims description 11
- 238000005259 measurement Methods 0.000 claims abstract description 22
- 238000005070 sampling Methods 0.000 claims abstract description 11
- 238000011156 evaluation Methods 0.000 claims abstract description 8
- 230000003287 optical effect Effects 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 230000017531 blood circulation Effects 0.000 description 3
- 238000002296 dynamic light scattering Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005286 illumination Methods 0.000 description 3
- 210000000601 blood cell Anatomy 0.000 description 2
- 210000004204 blood vessel Anatomy 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000010354 integration Effects 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000002123 temporal effect Effects 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 238000005311 autocorrelation function Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 210000004087 cornea Anatomy 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
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- Eye Examination Apparatus (AREA)
- Complex Calculations (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は、相関関数の評価方法、さらに詳細には、サン
プリング時間Δｔ秒毎に時系列入カバルスを計数し、そ
の時系列パルス信号の相関演算を行なうデジタル相関器
から得られる相関関数の収束性を評価する相関関数の評
価方法に関する。[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for evaluating a correlation function, and more specifically, a method for calculating the correlation of a time-series pulse signal by counting time-series input cavities at every sampling time Δt seconds. This invention relates to a correlation function evaluation method for evaluating the convergence of a correlation function obtained from a digital correlator.
［従来の技術］
運動している物体（例えば微粒子等）に光をあて、その
散乱先の光強度の時間的あるいは空間的変動を光検出し
、その信号を解析して物体に関する様々な情報を測定す
る方法が知られている．例えば，このような方法は、眼
底に所定径のレーザー光を照射し、眼底生体組織からの
散乱反射光によって観測面に形成されるレーザースペッ
クルパターンの変動を検出開口を介してスペックル光強
度変化として光電検出し、その光子相関関数を測定した
結果に基づいて、眼底組織の血流状態を測定する眼科診
断装置等に用いられている．このような動的光散乱技術
では，検出光強度をそれに比例した光電子パルス数の時
間的密度として検出し、パルス信号をデジタル相関器に
入力して、光子相関関数を測定する方法が一般的である
．これについては、例えばｒ ＰｈｏｔｏｎＣｏｒｒｅ
ｌａｔｉｏｎ Ｓｐｅｃｔｒｏｓｃｏｐｙ ａｎｄ Ｖ
ｅｌｏｃｉｍｅｔｒｙＪＰ１ｅｎｕｎ＋ Ｐｒｅｓｓ．
Ｎｅｗ Ｙｏｒｋ １９７７に示されている。[Prior art] A moving object (such as a particle) is illuminated with light, temporal or spatial fluctuations in the light intensity at the scattering destination are optically detected, and the signals are analyzed to obtain various information about the object. There are known methods to measure it. For example, in such a method, the fundus is irradiated with a laser beam of a predetermined diameter, and the intensity of the speckle light is measured through an aperture that detects fluctuations in the laser speckle pattern formed on the observation surface by scattered reflected light from the biological tissue of the fundus. It is used in ophthalmological diagnostic equipment, etc., which measures the blood flow state of the fundus tissue based on the results of photoelectric detection of changes and measurement of the photon correlation function. In such dynamic light scattering technology, the general method is to detect the detected light intensity as the temporal density of the number of photoelectron pulses proportional to it, input the pulse signal to a digital correlator, and measure the photon correlation function. be. For this, e.g. r PhotonCorre
lation Spectroscopy and V
elocimetryJP1enun+ Press.
New York 1977.
［発明が解決しようとする課題］
ところが測定される相関曲線は、検出光強度や．Ｍ乱先
のコヒーレンス、測定時間等種々の条件によってデータ
の積分化の度合いが異なり、これらの測定パラメータに
従って十分に収束した相関関数曲線が得られたり、ある
いは収束の十分でない相関関数曲線が得られたりする．
変動が大きい相関曲線は解析時に大きな誤差を含み、実
際は使用不可能である．そこで一般に、変動が小さく十
分収束した相関曲線を得るように測定条件の調整が行な
われる．その場合、十分収束したかどうかは、測定者が
容易に単一曲線で近似できるかどうかを目視で判断する
ことが多く非常にあいまいである。また所望の収束の程
度まで相関曲線を得るには、光量や測定時間等、どのよ
うな条件をどの程度変更すればよいかといった明確な目
安がなかった．前記の文献では相関曲線の収束に関する
各データの変動の様子と光量や、測定時間等との関係も
論じているが、実際の測定時にすぐに評価でき、かつ収
束の度合いを目視したものと直接結びつく表現がなされ
ていなかった。[Problems to be Solved by the Invention] However, the measured correlation curve does not depend on the detected light intensity or . The degree of data integration varies depending on various conditions such as the coherence of the M randomization destination and the measurement time, and depending on these measurement parameters, a sufficiently converged correlation function curve may be obtained, or a poorly converged correlation function curve may be obtained. Or. Correlation curves with large fluctuations contain large errors during analysis and are practically unusable. Therefore, measurement conditions are generally adjusted to obtain a sufficiently converged correlation curve with small fluctuations. In this case, it is very unclear whether sufficient convergence has occurred, as the measurer often visually determines whether or not it can be easily approximated by a single curve. Furthermore, there was no clear guideline as to what conditions, such as light intensity and measurement time, should be changed and how much they should be changed in order to obtain the correlation curve to the desired degree of convergence. The above-mentioned literature also discusses the relationship between the fluctuation of each data regarding the convergence of the correlation curve, the amount of light, the measurement time, etc. There was no expression that connected them.
従って、相関曲線は、測定のたびに異なる収束性を有し
、すなわち十分に積分化され収束性のよいデータと、そ
うでないデータとを比較論ずるという矛盾があった．こ
れは、はじめから測定誤差に対する条件の異なるデータ
間で比較することになり、正しい評価はできない．
従って，本発明はこのような問題点を解決するためにな
されたもので、相関関数曲線の収束性を定量的に評価す
ることが可能な相関関数の評価方法を提供することを課
題とする。Therefore, the correlation curve has different convergence properties each time it is measured, which creates a contradiction in that data that has been sufficiently integrated and has good convergence are compared with data that is not well integrated. This requires comparing data with different conditions for measurement error from the beginning, making it impossible to make accurate evaluations. Therefore, the present invention has been made to solve these problems, and an object of the present invention is to provide a correlation function evaluation method that can quantitatively evaluate the convergence of a correlation function curve.
［課題を解決するための手段］
本発明は，このような課題を解決するために、サンプリ
ング時間Δｔ秒毎に時系列入カパルスを計数し、その時
系列パルス信号の相関演算を行なうデジタル相関器から
得られる相関関数の収束性を評価する相関関数の評価方
法において、Ｔ秒間にわたって相関関数のデータ値を求
め、Ｃｓを相関関数データ値のベースラインの値に対す
る、相関関数データ値の最大値からベースラインの値を
差し引いた相関成分の最大値の比とし、また＜ｎ＞をＴ
秒間の測定時間内での単位サンプリング時間Δｔあたり
の平均パルス計数値として、Ｃｓ＜ｎ＞ Ｔ／ａｔ
で定まる相関関数データ値の変動率Ｒｆを求め、この変
動率に基づき相関関数の収束性の度合いを評価する構成
を採用した。[Means for Solving the Problems] In order to solve these problems, the present invention provides a digital correlator that counts time-series input pulses every sampling time Δt seconds and performs a correlation calculation on the time-series pulse signals. In the correlation function evaluation method for evaluating the convergence of the obtained correlation function, data values of the correlation function are obtained for T seconds, and Cs is calculated from the maximum value of the correlation function data value with respect to the baseline value of the correlation function data value. Let the ratio of the maximum value of the correlation component after subtracting the line value, and <n> be T
The fluctuation rate Rf of the correlation function data value determined by Cs<n>T/at is determined as the average pulse count value per unit sampling time Δt within the measurement time of seconds, and the convergence of the correlation function is calculated based on this fluctuation rate. We adopted a structure that evaluates the degree of
［作 用］
このような構成では、ディジタル相関器で得られる相関
関数の収束性を、その相関関数曲線を構成するデータの
変動率の度合いによって評価しそれが定式化される。こ
のように相関関数の評価値を変動率として定義するよう
にしているので、変動率に及ぼす各種測定条件の影響度
を明確にでき，正確な測定ができるようになる．
［実施例］
以下、図面に示す実施例に従い本発明を詳細に説明する
．以下の説明では、眼底カメラを使用して眼底血流を測
定する場合に得られる相関関数の収束性を例にして説明
する．
第１図は本発明に係る方法が実施される眼科診断装置全
体の概略図である．例えば、赤色の｝１ｅ−Ｎｅ（波長
６３２．８ｎｗ ）レーザー光源１からのレーザー光束
は、コンデンサレンズ１′を介し光強度を調整するため
の光量調整フィルター２を通過する。さらに、リレーレ
ンズ３、４を介して眼底カメラの眼底照明光学系に導か
れる．またリレーレンズ３と４の間には絞り５と６が設
置されており，これによって眼底におけるレーザー光の
照射領域の大きさと形状を選択するようになっている。[Operation] In such a configuration, the convergence of the correlation function obtained by the digital correlator is evaluated and formulated based on the degree of fluctuation rate of the data forming the correlation function curve. Since the evaluation value of the correlation function is defined as the rate of variation in this way, the influence of various measurement conditions on the rate of variation can be clarified and accurate measurements can be made. [Example] The present invention will be described in detail below based on the example shown in the drawings. In the following explanation, the convergence of the correlation function obtained when measuring fundus blood flow using a fundus camera will be explained as an example. FIG. 1 is a schematic diagram of the entire ophthalmological diagnostic apparatus in which the method according to the present invention is implemented. For example, a laser beam from a red}1e-Ne (wavelength: 632.8 nw) laser light source 1 passes through a light amount adjustment filter 2 for adjusting the light intensity via a condenser lens 1'. Furthermore, the light is guided to the fundus illumination optical system of the fundus camera via relay lenses 3 and 4. Further, apertures 5 and 6 are installed between the relay lenses 3 and 4, and are used to select the size and shape of the laser beam irradiation area on the fundus of the eye.
また、レーザー光源ｌの出射口にはシャッター７があり
、必要に応じて開閉する．リレーレンズ４で導かれたレ
ーザー光は、眼底照明光学系内のリングスリット８の環
状開口の一部に設置したミラー９で反射されて、眼底観
察撮影用光束が眼底に入射するのと同じ光路上に導かれ
る．このため，レーザー光はリレーレンズｌＯ、１１を
介して穴開きミラーｌ２で反射され，対物レンズ１３′
を介して被検眼ｌ３の角膜１３ａの上に一度集光した後
、拡散する状態で眼底Ｌ３ｂに達して，血管径に比べて
広い照射領域を形成する．この照射領域は、眼底カメラ
として用いられる照明光学系によって照明され、観察が
容易にされる．この観察光学系は、損影光源２４と同一
光軸上に配置された観察光源２２、コンデンサレンズ２
３、コンデンサレンズ２５，フィルター２７、ミラー２
６から構成される．レーザー光はこの観察撮影光束と同
じ光路に配置されるため、眼底カメラの左右、上下のス
ウィング機構や同視誘導機構を利用してレーザー光を眼
底の１３ｂの所望の位置に照射することができる。Further, there is a shutter 7 at the exit of the laser light source 1, which is opened and closed as necessary. The laser beam guided by the relay lens 4 is reflected by a mirror 9 installed in a part of the annular opening of the ring slit 8 in the fundus illumination optical system, and the same light as that of the light flux for fundus observation and photographing enters the fundus. He is led out onto the street. Therefore, the laser beam is reflected by the perforated mirror l2 via the relay lenses lO and 11, and the objective lens 13'
After the light is once focused on the cornea 13a of the eye L3 to be examined through the light, it reaches the fundus L3b in a diffused state and forms an irradiation area that is wider than the diameter of the blood vessel. This irradiation area is illuminated by an illumination optical system used as a fundus camera to facilitate observation. This observation optical system includes an observation light source 22 arranged on the same optical axis as a loss light source 24, and a condenser lens 2.
3. Condenser lens 25, filter 27, mirror 2
Consists of 6. Since the laser beam is placed on the same optical path as this observation/photographing light beam, the laser beam can be irradiated to a desired position on the fundus 13b by using the left/right and up/down swing mechanisms of the fundus camera and the same vision guidance mechanism.
なお、コンデンサレンズ２５とミラー２６間に配置され
るフィルター２７は、波長分離フィルターとして構成さ
れるので、観察、搬影光に含まれる赤色成分はカットさ
れる．
レーザー光が眼底血管内を移動する血球で散乱されて生
ずるスペックル光は、再び対物レンズ１３′で受光され
、穴開きミラーｌ２を通過して撮影レンズｌ４ならびに
波長分離ミラー１５に到達する．この波長分離ミラーｌ
５は、フィルター２７と同様な分光特性を有しており、
赤色域の波長の光の大部分が反射され、それ以外の光は
透過するので、Ｈｅ−Ｎｅレーザー光によって生じたス
ペックル光（赤色）は、大部分が反射される．この反射
光はレンズ１６で一度、像面３５に結像されさらに顕微
鏡光学系Ｉ９の対物レンズ１９ａと接眼レンズ１９ｂを
介して拡大される．拡大像は検出開口２０を通過し、再
び集光レンズ２１で集められ、光電子増倍管（フォトマ
ル）４０で検出される。光電子増倍管４０の前にはシャ
ッター４０′が配置され、開放時に得られるそこからの
出力信号は信号処理回路５０に入力される。Note that since the filter 27 disposed between the condenser lens 25 and the mirror 26 is configured as a wavelength separation filter, the red component contained in the observation and projection light is cut. Speckle light generated when the laser light is scattered by blood cells moving in the fundus blood vessels is received again by the objective lens 13', passes through the perforated mirror l2, and reaches the photographing lens l4 and the wavelength separation mirror 15. This wavelength separation mirror
5 has the same spectral characteristics as the filter 27,
Most of the light with wavelengths in the red region is reflected, and other light is transmitted, so most of the speckle light (red) generated by the He-Ne laser light is reflected. This reflected light is once formed into an image on the image plane 35 by the lens 16, and further magnified via the objective lens 19a and the eyepiece lens 19b of the microscope optical system I9. The magnified image passes through the detection aperture 20, is collected again by the condenser lens 21, and is detected by a photomultiplier tube (photomultiplier) 40. A shutter 40' is arranged in front of the photomultiplier tube 40, and an output signal from the shutter 40' obtained when the shutter is opened is inputted to a signal processing circuit 50.
この信号処理回路５０は第２図に示すように増幅器５２
、ディスクリミネータ５３、デジタル相関器５４、マイ
クロコンピュータ５５から構成される．
一方，波長分離ミラーｌ５を通過した光は、リレーレン
ズ２８，跳ね上げミラー２９，ミラー３０、レチクル３
１、接眼レンズ３３を介して観察でき、また撮影フィル
ム３２で盪影できるように構成されている．
このような構成において、光電子増倍管４０で検出され
た信号は、例えば、眼底の血球移動にともない時間とと
もに変動するスペックル信号であり，第３図（ａ）のよ
うにＩ（ｔ）で表せる．測定時間で平均した時の直流分
に相当する平均値は＜ｒ＞である． Ｉ （ｔ）は、
第２図にて増幅器５２で増幅され、ディスクリミネータ
５３で入射強度に応じた数のパルス列を発生する．これ
は第３図（ｂ）に図示したような波形となり、強い光で
は単位時間あたりのパルス数密度が太き《なる．パルス
信号はデジタル相関器５４にて．第３図（Ｃ）のように
、あらかじめ設定したサンプリング時間Δｔごとにパル
ス数を計数し、それぞれパルス計数値ｎｌ．ｎ２．ｎ３
．・−・ｎｉを求めてい《．これらの計数データを基に
デジタル相関器５４は自己相関関数ｇ（ＣΔτ）
ｇ（ＣΔτ）＝Σｎ ｉ ＊ ｎ ｉ＋ｃ
（ １ ）を計算する．
この結果が第４図のように相関関数曲線となって表示さ
れる．この時データの積分化が十分でないと第４図のよ
うにプロットデー夕はある幅内に広がって変動したもの
となる，（ｌ）式の値は、測定時間を長くし、Ｎを太き
《とればとる程大きくなり、第４図においてデータが積
み上げられていくことになる．第４図でベースラインの
高さは〈ｎ〉２となる．〈ｎ〉はＴ秒間で合計ｍｓ＝Ｔ
／ΔＬ個のｎｉデータの平均値、すなわちｌサンプリン
グ時間△ｔあたりの平均パルス数を示す。ベースライン
から上の信号成分の高さは〈Δｎｓ２＞で示される。〈
Δｎｓ２＞はｎｉのゆらぎ成分△ｎ ｓｉ＝ ｎ ｓｉ
− ＜ ｎ ＞の分散である．さらにデータの変動し
ている広がりの実効幅は〈Δｎｅ ” ＞で示される６
〈Δｎｅ２＞は理想的に一定の光強度を検出しても、光
子計数値ｎｅｉは平均値＜ｎｅ＞のまわりにある幅をも
って変動することを表しており、光電子計数ゆらぎの分
散を示す。This signal processing circuit 50 includes an amplifier 52 as shown in FIG.
, a discriminator 53, a digital correlator 54, and a microcomputer 55. On the other hand, the light that has passed through the wavelength separation mirror l5 is transmitted through the relay lens 28, flip-up mirror 29, mirror 30, and reticle 3.
1. It is constructed so that it can be observed through an eyepiece lens 33 and can be photographed using a photographic film 32. In such a configuration, the signal detected by the photomultiplier tube 40 is, for example, a speckle signal that fluctuates over time as blood cells move in the fundus, and as shown in FIG. It can be expressed. The average value corresponding to the DC component when averaged over the measurement time is <r>. I (t) is
In FIG. 2, it is amplified by an amplifier 52, and a discriminator 53 generates a number of pulse trains corresponding to the incident intensity. This results in a waveform as shown in Figure 3(b), where the density of the number of pulses per unit time becomes thick with strong light. The pulse signal is processed by a digital correlator 54. As shown in FIG. 3(C), the number of pulses is counted every preset sampling time Δt, and each pulse count value nl. n2. n3
．．・-・I'm looking for ni《. Based on these count data, the digital correlator 54 calculates an autocorrelation function g(CΔτ) g(CΔτ)=Σni*ni+c
Calculate (1). This result is displayed as a correlation function curve as shown in Figure 4. At this time, if the integration of the data is not sufficient, the plot data will spread and fluctuate within a certain range as shown in Figure 4.The value of equation (l) is determined by increasing the measurement time and thickening N. 《The more you take, the larger it becomes, and the data will accumulate in Figure 4. In Figure 4, the height of the baseline is <n>2. <n> is the total ms=T in T seconds
/ΔL ni data, ie, the average number of pulses per l sampling time Δt. The height of the signal component above the baseline is indicated by <Δns2>. <
Δns2> is the fluctuation component of ni Δn si= n si
− is the variance of <n>. Furthermore, the effective width of the varying spread of the data is denoted by 〈Δne''〉6
<Δne2> represents that even if ideally constant light intensity is detected, the photon count value nei fluctuates within a certain range around the average value <ne>, indicating the dispersion of photoelectron count fluctuation.
通常、相関曲線はベースラインを差し引き、ベースライ
ンから上の部分を第５図のように表示するので、測定者
がデータの収束性の度合いを定量化するときは、相関部
分の曲線の高さ〈Δｎｓ ２＞に対するデータの変動幅
〈Δｎｅ２＞の割り合いをみればよい．それを変動率Ｒ
ｆとして、次式で定義する。Normally, a correlation curve is calculated by subtracting the baseline and displaying the part above the baseline as shown in Figure 5. When measuring the degree of convergence of data, the measurer needs to calculate the height of the curve in the correlation part. Just look at the ratio of the data fluctuation width <Δne2> to <Δns 2>. It is the fluctuation rate R
f is defined by the following equation.
くΔｎｅ２＞
Ｒｆ＝ ×１００（％） （２）くΔｎ
ｓ２＞
（２）式の分子〈Δｎｅ”＞は光電子計数ゆらぎの確率
分布がポアソン過程に従う時、
くΔｎ ｅ ” ＞ ＝ Ｆ石１＜ ｎ ＞
（ ３ ）と表わせる。また分母〈Δｎｓ”＞は
〈Δｎｓ ” ＞＝ｍｓＣｓ＜ｎ＞２ （４）と
なる．ここでＣｓは入力信号のコントラストＣ＝Ｆてτ
Ｉ”＞／＜Ｉ＞の２乗した値であり、第４図における〈
Δｎｓ”＞／＜ｎ＞”の比となる。なお△ＩはΔＩ＝Ｉ
（ｔ）−＜Ｉ＞である。Δne2> Rf= ×100(%) (2) Δn
s2> The numerator 〈Δne''〉 of equation (2) is when the probability distribution of photoelectron count fluctuation follows the Poisson process,
It can be expressed as (3). Also, the denominator <Δns''> becomes <Δns''>=msCs<n>2 (4). Here, Cs is the contrast of the input signal C=F τ
It is the square value of I''>/<I>, and is the value of <
The ratio is Δns”>/<n>”. Note that △I is ΔI=I
(t)-<I>.
これらの関係から最終的にＲｆは
ｌ００
Ｒｆ＝ （％）
（５）ｃｓ＜ｎ＞５７Ｔ『
となる．
（５）式によって、第５図のように測定した相関関数曲
線の収束性を評価できることが理解できる．Ｒｆ（％）
は第５図のように曲線の高さを１００％とした時の変動
幅の割合をバーセントで直接示しており、目視観測の結
果を直接に表現できる数値として大変便利で有効である
。From these relationships, the final Rf is l00 Rf= (%)
(5) cs<n>57T' becomes. It can be seen that the convergence of the correlation function curve measured as shown in Figure 5 can be evaluated using equation (5). Rf (%)
As shown in Figure 5, it directly shows the percentage of the fluctuation range when the height of the curve is taken as 100%, and is very convenient and effective as a numerical value that can directly express the results of visual observation.
変動率Ｒｆのほぼ等しいデータは相関曲線か例えばｌか
らｌ／ｅに落ちる点の遅れ時間である時間相関長τＣを
求める時や、曲線の形状等を見る場合にも、ほぼ同じ誤
差条件で比較できることになる。またＲｆが例えば１０
％以下のデータを採用し、他は不採用という基準を設け
ておけば、測定した相関曲線に対し、（５）式の計算を
第２図のマイクロコンピュータ５５で行ない、その場で
変動率Ｒｆを調べ、必要なもののみ記録あるいは解析す
るような作業をあいまいな目視観測ではなく所定の標準
に従って行なうことができ結果の客観性を増大させるこ
とができる．
（５）式は更に、相関関数の収束性の度合いを評価する
基準となる変動率が、測定時間Ｔ，サンプリング時間Δ
ｔ．１サンプリング時間Δｔあたりの平均光電子パルス
計数＜ ｎ ＞、人力信号のコントラストの２乗を示す
Ｃｓによってどのように決定されるかを示しているので
，これらのパラメータや測定条件がわかっていれば、変
動率Ｒｆが何％になるかは測定を行なう前から評価可能
である。また所望のＲｆを得るには、どの条件をどの程
度改とすればよいかも（５）式から容易に求めることが
できる．例えば、（５）式において検出光量が２倍にな
れば、＜ｎ＞も２倍になるのでＲ『は１／２に減少し、
収束性は２倍よくなる。Data with approximately the same rate of fluctuation Rf can be compared under approximately the same error conditions when calculating the time correlation length τC, which is the delay time at the point where the correlation curve falls from l to l/e, or when looking at the shape of the curve, etc. It will be possible. Also, Rf is, for example, 10
% or less, and other data are rejected, the microcomputer 55 in FIG. 2 calculates the equation (5) for the measured correlation curve, and the fluctuation rate Rf can be calculated on the spot. The objectivity of the results can be increased because tasks such as investigating and recording or analyzing only the necessary items can be performed according to predetermined standards rather than vague visual observations. Equation (5) further shows that the fluctuation rate, which is the standard for evaluating the degree of convergence of the correlation function, is determined by the measurement time T and the sampling time Δ
t. It shows how it is determined by the average photoelectron pulse count <n> per sampling time Δt and Cs, which is the square of the contrast of the human input signal, so if these parameters and measurement conditions are known, It is possible to evaluate what percentage the fluctuation rate Rf will be before performing the measurement. Furthermore, to obtain the desired Rf, it can be easily determined from equation (5) which conditions should be modified and by what degree. For example, in equation (5), if the detected light amount doubles, <n> also doubles, so R' decreases to 1/2,
Convergence is twice as good.
一方、それに対して測定時間ＴによってＲｆを１／２に
するためには測定時間Ｔを４倍長《してやる必要がある
ことがわかる．
動的光散乱で光子相関法を用いる場合、本発明方法によ
って収束性を定量的に評価し得るが、特に光強度が微弱
な場合は、曲線が十分に収束しないため，収束性の評価
は非常に重要で（５）式の果たす役割は大きい。On the other hand, it can be seen that in order to reduce Rf to 1/2 by measuring time T, it is necessary to increase the measuring time T by four times. When using the photon correlation method in dynamic light scattering, convergence can be quantitatively evaluated by the method of the present invention, but the evaluation of convergence is extremely difficult, especially when the light intensity is weak, as the curve does not converge sufficiently. This is important, and equation (5) plays a large role.
例えば、第１図に示した眼科測定装置おいて、眼底にレ
ーザー光を照射して得られる散乱スペックルパターンの
変動を検出し、光子相関曲線から、眼底の血流等種々の
医学情報を得ようとする時、レーザー照射パワーや測定
時間は安全性の立場から一定の制限条件があり、また眼
底からのスペックルパターンのコントラストも生体特有
の性質をもっていて、測定者が自由に変えることができ
ない。こうした条件の中で測定すべき相関曲線の収束性
がどの程度になるかなどの評価が定量的に行なえること
は極めて好ましいことである，というのは、検出光量、
信号コントラスト、測定時間、サンプリングタイム等を
どの程度に設定すれば良好な結果が得られるかを容易に
評価できるからである。またスペックルパターンのスペ
ッックル平均径に対し、検出開口径を大きくしてやれば
、光量は多く検出できるが、信号のコントラストは低下
するなどの問題もあるが、これも（５）式により，最も
小さくなる変動率Ｒｆを与える条件を見い出せば，最適
検出開口径の決定にも利用できるため、本発明の効果は
非常に大きい．［発明の効果］
以上説明したように、本発明によれば、相関関数データ
値の変動串Ｒｆを求め、この変動率に基づき相関関数の
収束性の度合いを評価するようにしているので、相関関
数の評価を定量的に行なうことができ，良質の測定結果
を得るための測定パラーメタの設定を容易にできるとい
う極めて優れた効果が得られる。For example, the ophthalmological measuring device shown in Figure 1 detects fluctuations in the scattered speckle pattern obtained by irradiating the fundus with laser light, and obtains various medical information such as blood flow in the fundus from the photon correlation curve. When attempting to perform measurements, there are certain limitations on the laser irradiation power and measurement time from a safety standpoint, and the contrast of the speckle pattern from the fundus also has characteristics unique to living organisms, and cannot be changed freely by the measurer. . It is extremely desirable to be able to quantitatively evaluate the degree of convergence of the correlation curve to be measured under these conditions.
This is because it is possible to easily evaluate to what extent signal contrast, measurement time, sampling time, etc. should be set to obtain good results. In addition, if the detection aperture diameter is made larger than the speckle average diameter of the speckle pattern, a large amount of light can be detected, but there are also problems such as a decrease in signal contrast, but this is also minimized according to equation (5). If the conditions that give the fluctuation rate Rf are found, it can also be used to determine the optimum detection aperture diameter, so the effects of the present invention are very large. [Effects of the Invention] As explained above, according to the present invention, the fluctuation rate Rf of the correlation function data value is obtained and the degree of convergence of the correlation function is evaluated based on this fluctuation rate. This has the extremely advantageous effect of being able to quantitatively evaluate functions and making it easy to set measurement parameters to obtain high-quality measurement results.
第１図は、本発明方法が用いられる眼科装置の構成を示
した構成図、第２図は、信号処理装置の構成を示したブ
ロック図、第３図（ａ）から（ｃ）は、人力信号の相関
処理を説明する信号波形図、第４図および第５図は相関
関数の変動を示した説明図である。
４０・一光電子増倍管
５０−・・信号処理装置
５４・−デジタル相関器
５５・・−マイクロコンピュータFIG. 1 is a block diagram showing the structure of an ophthalmological apparatus in which the method of the present invention is used, FIG. 2 is a block diagram showing the structure of a signal processing device, and FIGS. 3(a) to (c) are human-powered Signal waveform diagrams illustrating signal correlation processing, and FIGS. 4 and 5 are explanatory diagrams showing fluctuations in correlation functions. 40 - Photomultiplier tube 50 - Signal processing device 54 - Digital correlator 55 - Microcomputer
Claims (1)
数し、その時系列パルス信号の相関演算を行なうデジタ
ル相関器から得られる相関関数の収束性を評価する相関
関数の評価方法において、Ｔ秒間にわたって相関関数の
データ値を求め、Ｃｓを相関関数データ値のベースライ
ンの値に対する、相関関数データ値の最大値からベース
ラインの値を差し引いた相関成分の最大値の比とし、ま
た＜ｎ＞をＴ秒間の測定時間内での単位サンプリング時
間Δｔあたりの平均パルス計数値として、 ▲数式、化学式、表等があります▼ で定まる相関関数データ値の変動率Ｒｆを求め、 この変動率に基づき相関関数の収束性の度合いを評価す
ることを特徴とする相関関数の評価方法。[Claims] 1) A correlation function evaluation method for evaluating the convergence of a correlation function obtained from a digital correlator that counts time-series input pulses every sampling time Δt seconds and performs a correlation operation on the time-series pulse signals. , calculate the data value of the correlation function for T seconds, and let Cs be the ratio of the maximum value of the correlation component obtained by subtracting the baseline value from the maximum value of the correlation function data value to the baseline value of the correlation function data value, In addition, where <n> is the average pulse count value per unit sampling time Δt within the measurement time of T seconds, find the fluctuation rate Rf of the correlation function data value determined by ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and this fluctuation A method for evaluating a correlation function, characterized by evaluating the degree of convergence of the correlation function based on a rate.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1051953A JPH02231673A (en) | 1989-03-06 | 1989-03-06 | Evaluating method for correlation function |
| DE69011158T DE69011158T2 (en) | 1989-03-06 | 1990-02-28 | Diagnostic device in ophthalmology. |
| EP90302102A EP0386927B1 (en) | 1989-03-06 | 1990-02-28 | Ophthalmological diagnosis apparatus |
| US07/488,713 US5074307A (en) | 1989-03-06 | 1990-03-05 | Ophthalmological diagnosis apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1051953A JPH02231673A (en) | 1989-03-06 | 1989-03-06 | Evaluating method for correlation function |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02231673A true JPH02231673A (en) | 1990-09-13 |
Family
ID=12901238
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1051953A Pending JPH02231673A (en) | 1989-03-06 | 1989-03-06 | Evaluating method for correlation function |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02231673A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016005525A (en) * | 2014-05-30 | 2016-01-14 | ソニー株式会社 | Fluid analysis device, fluid analysis method, program and fluid analysis system |
| US10690593B2 (en) | 2015-11-13 | 2020-06-23 | Horiba, Ltd. | Sample analyzer and recording medium recording sample analysis program |
-
1989
- 1989-03-06 JP JP1051953A patent/JPH02231673A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2016005525A (en) * | 2014-05-30 | 2016-01-14 | ソニー株式会社 | Fluid analysis device, fluid analysis method, program and fluid analysis system |
| US10690593B2 (en) | 2015-11-13 | 2020-06-23 | Horiba, Ltd. | Sample analyzer and recording medium recording sample analysis program |
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