JPH10160711A - Photoacoustic signal measuring device - Google Patents
Photoacoustic signal measuring deviceInfo
- Publication number
- JPH10160711A JPH10160711A JP8321363A JP32136396A JPH10160711A JP H10160711 A JPH10160711 A JP H10160711A JP 8321363 A JP8321363 A JP 8321363A JP 32136396 A JP32136396 A JP 32136396A JP H10160711 A JPH10160711 A JP H10160711A
- Authority
- JP
- Japan
- Prior art keywords
- light
- photoacoustic signal
- signal
- wavelength
- measurement
- 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.)
- Granted
Links
Landscapes
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Measuring And Recording Apparatus For Diagnosis (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は光音響信号測定装置
に関し、より詳しくは例えば近赤外の波長を好ましく用
い、水分量をin vivo測定するに適した光音響信号測定
装置に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoacoustic signal measuring device, and more particularly to a photoacoustic signal measuring device which preferably uses, for example, a near-infrared wavelength and is suitable for measuring the amount of water in vivo.
【０００２】[0002]
【従来の技術】対象物質に含まれる被測定物質を測定す
る方法には種々のものがあるが、近年注目されているも
のとして光音響分光法（ＰＡＳ）がある。この方法は、
試料に断続光を照射し、試料が吸収した光のエネルギー
を音波として検出するものであり、薬剤の経皮吸収の測
定や免疫反応の分析など各種の測定分野において、散乱
光の影響を受けずに非破壊で分析可能な方法として期待
されている。2. Description of the Related Art There are various methods for measuring a substance to be measured contained in a target substance, and a photoacoustic spectroscopy (PAS) has recently attracted attention. This method
It irradiates the sample with intermittent light and detects the energy of the light absorbed by the sample as sound waves.It is not affected by scattered light in various measurement fields such as measurement of transdermal absorption of drugs and analysis of immune reactions. It is expected to be a nondestructive and analytical method.
【０００３】ところでＰＡＳに用いられるセルとして
は、試料をセル内に入れる密閉型と、セルの開放端部を
試料に押し当てて密閉状態とする開放型とがある。密閉
型の場合も開放型の場合も、試料から得られる音波を正
確に検出し増幅することが必要であるが、密閉型の場合
は信号の検出が比較的容易である反面、in vivo測定が
不可能であるという欠点がある。開放型の場合には、in
vivo、in situ測定が可能であるが、環境雑音や皮膚に
押し当てた場合の脈拍といった、バックグラウンドノイ
ズの影響を受けやすく、光音響信号を正確に測定するこ
とが困難であるといった問題がある。There are two types of cells used for the PAS: a closed type in which a sample is placed in the cell, and an open type in which the open end of the cell is pressed against the sample to make it closed. It is necessary to accurately detect and amplify the sound waves obtained from the sample in both the closed type and the open type, but in the closed type, signal detection is relatively easy, but in vivo measurement is difficult. The disadvantage is that it is not possible. In the case of open type, in
In vivo and in situ measurement is possible, but there is a problem that it is easily affected by background noise such as environmental noise and pulse when pressed against the skin, and it is difficult to measure photoacoustic signal accurately. .
【０００４】特公平５−14219号は光音響測定装置に関
し、セル内の試料を波長と変調周波数の両者が異なる、
反応生成物と未反応物質のそれぞれに対応する２以上の
励起光で照射し、検出された光音響信号の強度差に基づ
き反応生成物を定量する技術、或いはセル内の試料を単
一波長、単一変調周波数の励起光で照射し、光音響信号
を試料の反応過程における２以上の時刻において検出
し、検出信号の強度差に基づいて反応生成物を定量する
技術を開示している。これらの技術はバックグラウンド
補正を不要とするものであるが、in vivoでの適用を考
慮したものではなく、また２以上の励起光を用いる場合
には変調周波数を異ならせることが必要であり、単一の
励起光を用いる場合には反応過程をフォローし、しかも
反応速度の関数表現を持っていることが必要である。[0004] Japanese Patent Publication No. 5-14219 relates to a photoacoustic measurement apparatus, in which a sample in a cell is different in both wavelength and modulation frequency.
A technique of irradiating with two or more excitation lights corresponding to each of the reaction product and the unreacted substance, and quantifying the reaction product based on the difference in the intensity of the detected photoacoustic signal, or a sample in the cell at a single wavelength, There is disclosed a technique of irradiating with excitation light having a single modulation frequency, detecting a photoacoustic signal at two or more times in a reaction process of a sample, and quantifying a reaction product based on a difference in intensity of the detection signal. Although these techniques do not require background correction, they do not consider application in vivo, and when using two or more excitation lights, it is necessary to make the modulation frequency different, When using a single excitation light, it is necessary to follow the reaction process and have a function expression of the reaction rate.
【０００５】特公平６−21861号は、光音響分光装置に
関し、直流でバイアスした交流で半導体レーザーを駆動
し、連続光を光源とする際のチョッパやビームスプリッ
タを不要化する技術を開示している。しかしながらこの
技術も密閉型のセルに関するものであり、in vivoでの
適用は考慮されていない。Japanese Patent Publication No. 6-21861 relates to a photoacoustic spectroscopy device and discloses a technique for driving a semiconductor laser with an alternating current biased with a direct current to eliminate the need for a chopper or a beam splitter when using continuous light as a light source. I have. However, this technique also relates to a closed cell, and is not considered for in vivo application.
【０００６】特開平１−191040号は開放型のセルに関す
るものであり、測定側セルと光源を持たない参照側セル
の差動をとることにより、バックグラウンドノイズを低
減させることを意図している。この場合、セルは長さ調
節可能な共鳴構造とされ、共鳴によって光音響信号の強
度の向上が図られると共に、測定側セルの試料押着部近
傍を光透過性材料から形成することによって、反射光に
よるノイズの低減が期待されている。またこの技術の改
良として、特開平４−357440号は、試料室をライトガイ
ドと一体のものとして、セルのデッドボリュームを必要
最小限とすることを教示している。JP-A-1-191040 relates to an open-type cell, and is intended to reduce background noise by taking a differential between a measuring cell and a reference cell having no light source. . In this case, the cell has a resonance structure whose length can be adjusted, so that the intensity of the photoacoustic signal is improved by resonance, and the vicinity of the sample pressing portion of the measurement-side cell is formed of a light-transmitting material, so that the reflection is achieved. Reduction of noise due to light is expected. As an improvement of this technique, Japanese Patent Application Laid-Open No. 4-357440 teaches that a sample chamber is integrated with a light guide to minimize the dead volume of a cell.
【０００７】さらに、ＰＡＳでは変調周波数を変化させ
ることにより、深さ方向の情報を得られることが知られ
ている。これは、照射光の変調周波数に依存する熱拡散
長によって測定深さが左右されているためである。特開
平２−83481号は、所定深さにおける情報を映像化する
ために、変調光（He-Neレーザー）を２種以上の変調周
波数で光強度変調し、検出した光音響信号の強度比又は
位相差に基づいて映像化を行うことを開示している。Further, it is known that in the PAS, information in the depth direction can be obtained by changing the modulation frequency. This is because the measurement depth is influenced by the thermal diffusion length depending on the modulation frequency of the irradiation light. Japanese Patent Application Laid-Open No. 2-83481 discloses that in order to visualize information at a predetermined depth, modulated light (He-Ne laser) is light-intensity-modulated at two or more kinds of modulation frequencies, and the intensity ratio of a detected photoacoustic signal or It discloses that imaging is performed based on a phase difference.
【０００８】[0008]
【発明が解決しようとする課題】皮膚（角質層）の水分
量は、肌の状態と関係があると考えられているため、化
粧品や香粧品の開発、店頭での肌診断などにおいて、皮
膚の水分を測定することが行われている。これらの測定
は電気伝導度を測定する、いわゆるコンダクタンス法を
基礎とするものであるが、これは測定が簡便である反
面、電解質の影響を受けやすく定量性に欠けるといった
問題点がある。そこで光音響分光法をこうした皮膚の水
分量測定に応用することが試みられているが、上記に従
来技術に関して記述したように、開放型のセルを用いて
in vivo、in situ測定が可能なものは数少ない。また開
放型のセルを用いる場合は、前に述べたように環境雑音
や脈拍といったバックグラウンドノイズのために測定が
難しいという問題に対処しなければならないが、特開平
１−191040号及び特開平４−357440号の技術は、変調周
波数に合わせて共鳴周波数を調節しなければならず、ま
た紫外光を用いた測定を主体とするため、皮膚に対する
影響を無視することができない。特開平１−191040号で
は1600nmの近赤外波長を用いて水分量を測定する可能性
が示されているが、そこに開示されているように１波長
で測定した場合、バックグラウンドの補正が不十分でセ
ルを皮膚に押し当てる力の差によって信号の強度が変化
するという問題がある。本発明の一つの課題は、これら
の問題点を解決し、皮膚の水分量をin vivo、in situで
簡便に高精度で測定することのできる、新規な光音響信
号測定装置を提供することである。Since the water content of the skin (the stratum corneum) is considered to be related to the condition of the skin, it has been used in the development of cosmetics and cosmetics, skin diagnosis at stores, and the like. Measuring moisture has been performed. These measurements are based on the so-called conductance method of measuring the electric conductivity, but this method has a problem that it is easy to measure, but is susceptible to the electrolyte and lacks quantitativeness. Attempts have been made to apply photoacoustic spectroscopy to such skin moisture measurement, but as described above with reference to the prior art, using an open cell
Only a few are capable of in vivo and in situ measurements. When an open cell is used, it is necessary to deal with the problem that measurement is difficult due to background noise such as environmental noise and pulse as described above. In the technique of -357440, the resonance frequency must be adjusted in accordance with the modulation frequency, and since the measurement is mainly performed using ultraviolet light, the effect on the skin cannot be ignored. Japanese Patent Application Laid-Open No. 1-191040 discloses the possibility of measuring the water content using a near-infrared wavelength of 1600 nm. However, when the measurement is performed at one wavelength as disclosed therein, the background correction is not performed. There is a problem that the strength of the signal changes due to the insufficient force of pressing the cell against the skin. One object of the present invention is to solve these problems and provide a novel photoacoustic signal measurement device that can easily and accurately measure the water content of skin in vivo and in situ. is there.
【０００９】また、ＰＡＳによれば変調周波数を変化さ
せることによって深さ方向の情報を得ることができる
が、これにより得られる情報は表面から測定深さまでの
情報が足し合わされた形でのものであり、測定深さ自体
における情報のみ、即ち深さ方向の濃度分布を求めるの
は困難である。従来技術として示した特開平２−８３４
８１号は、可視領域の波長（Ｈｅ−Ｎｅレーザー）を用
いて深さ方向の情報の映像化を行う可能性を示している
が、近赤外波長を用いた場合には吸光係数が小さいため
感度が悪く、皮膚のin vivo測定には適していないと考
えられる。本発明の別の課題は、このような問題点を克
服して、所定深さにおける情報、特に皮膚の水分量に関
する情報を適切に得ることのできる光音響信号測定装置
を提供することである。なお、本発明は以上に述べた皮
膚の水分量の測定の他、各種薬剤の経皮吸収や高分子物
質中の水分、界面活性剤等の測定にも有効に用いること
ができることは言うまでもない。Further, according to the PAS, information in the depth direction can be obtained by changing the modulation frequency, and the information obtained by this is a form in which information from the surface to the measurement depth is added. Therefore, it is difficult to obtain only the information at the measurement depth itself, that is, the density distribution in the depth direction. JP-A-2-834 shown as a prior art
No. 81 shows the possibility of visualizing information in the depth direction using a wavelength in the visible region (He-Ne laser). However, when a near-infrared wavelength is used, the absorption coefficient is small. It is considered to be unsuitable for in vivo measurement of skin due to poor sensitivity. Another object of the present invention is to provide a photoacoustic signal measurement device capable of appropriately obtaining information at a predetermined depth, in particular, information on the water content of the skin, by overcoming such problems. In addition, it goes without saying that the present invention can be effectively used not only for the measurement of the water content of the skin described above but also for the measurement of the transdermal absorption of various drugs and the measurement of the water content and the surfactant in the polymer substance.
【００１０】[0010]
【課題を解決するための手段】本発明により提供される
光音響信号測定装置は、測定波長の光と参照波長の光を
照射する光源手段と、測定波長の光と参照波長の光を少
なくとも１種の変調信号でそれぞれ変調し、セルへと交
互に導く１以上の時間帯を有する変調手段とを含む。光
源手段は測定波長の光を照射する第一の光源と参照波長
の光を照射する第二の光源を少なくとも有することがで
き、変調手段は第一の光源及び第二の光源を少なくとも
１種の変調信号で交互に駆動する１以上の時間帯を有す
る駆動手段を含むことができる。セルは開放端部を有
し、照射された光を合波手段を介して、被測定物質を含
む対象物に差し向ける。測定波長の光は、被測定物質に
特異な吸収波長を有するものであることが好ましく、被
測定物質に応じて変化させる必要があるが、例えば対象
物が皮膚であり、被測定物質が皮膚中の水分である場合
には、水に特異な吸収波長を有する（例えばOH変角の倍
音など）光が好ましい。参照波長の光は、被測定物質に
よって少なくとも特異的に吸収されない波長のものであ
ればどのような波長のものでも構わないが、測定波長が
近赤外領域にあれば、通常はその近傍で選択される。こ
れらの光を照射する光源は、波長スペクトルの比較的狭
い光源で、目的の波長を有するものであれば何れでもよ
く、例えば連続光を有する光源から分光器やフィルタを
用いて所望の光を得ることもできるが、この場合はチョ
ッパーを用いて変調を行うことになる。そのため光源と
してはレーザー光源であるのが好ましく、半導体レーザ
ーが特に好ましい。半導体レーザーを用いた場合には変
調周波数を容易に変化させることができると共に、光源
自体の高出力化が図られる。こうした場合に二つの光源
を駆動する変調信号は相互に同一である必要は必ずしも
ないが、参照波長の光による補正をより効率よく行うた
めには、両者の差は±10％以内、好ましくは通常の許容
範囲内で同一であるのが特に好ましい。即ち第一の光源
と第二の光源は種々の変調周波数で駆動可能であるが、
ある時点においては両者が許容範囲内で同一であること
が好ましい。但し、駆動手段は第一の光源と第二の光源
を少なくとも１種の変調信号で交互に駆動する１以上の
時間帯を有することが必要である。即ち二つの光源は部
分的に同時に駆動されてもよいが、好ましい例では、あ
る変調周波数で第一の光源を一定時間駆動し（その間は
第二の光源は停止）、次いで同一の変調周波数で第二の
光源を一定時間駆動する（この時第一の光源は停止）。
これを必要回数繰り返した後、必要に応じて変調周波数
を変化させ、同様の測定を継続する。なお上記の一定時
間は目的に応じて適宜選択することができるが、例えば
0.1〜60秒、好ましくは１〜10秒程度である。またこの
測定時間は第一の光源と第二の光源で同じにする必要は
必ずしもない。変調周波数は、所望とする測定深さに応
じて適宜選択される。According to the present invention, there is provided a photoacoustic signal measuring apparatus provided with a light source for irradiating light having a measurement wavelength and light having a reference wavelength, and having at least one light having the measurement wavelength and light having the reference wavelength. And modulating means having one or more time zones, each modulating with a different type of modulation signal and alternately leading to a cell. The light source means may have at least a first light source for irradiating light of the measurement wavelength and a second light source for irradiating light of the reference wavelength, and the modulation means includes at least one type of the first light source and the second light source. A driving means having one or more time zones alternately driven by the modulation signal can be included. The cell has an open end, and directs the irradiated light to the object containing the substance to be measured via the multiplexing means. The light at the measurement wavelength preferably has an absorption wavelength specific to the substance to be measured, and needs to be changed according to the substance to be measured.For example, the target is skin, and the substance to be measured is in the skin. In the case of water, light having an absorption wavelength peculiar to water (for example, overtone of OH bending angle) is preferable. The reference wavelength light may be of any wavelength as long as it is at least not specifically absorbed by the substance to be measured, but if the measurement wavelength is in the near infrared region, it is usually selected in the vicinity. Is done. The light source for irradiating these lights is a light source having a relatively narrow wavelength spectrum and may be any light source having a desired wavelength. For example, a desired light is obtained from a light source having continuous light using a spectroscope or a filter. However, in this case, modulation is performed using a chopper. Therefore, the light source is preferably a laser light source, and a semiconductor laser is particularly preferable. When a semiconductor laser is used, the modulation frequency can be easily changed, and the output of the light source itself can be increased. In such a case, the modulation signals for driving the two light sources do not necessarily have to be the same as each other, but in order to perform the correction with the light of the reference wavelength more efficiently, the difference between the two is within ± 10%, preferably normal. It is particularly preferred that they are the same within the allowable range of That is, the first light source and the second light source can be driven at various modulation frequencies,
At some point, it is preferred that they are identical within an acceptable range. However, the driving means needs to have one or more time zones in which the first light source and the second light source are alternately driven by at least one type of modulation signal. That is, the two light sources may be partially driven at the same time, but in a preferred example, the first light source is driven at a certain modulation frequency for a certain period of time (while the second light source is stopped), and then at the same modulation frequency. The second light source is driven for a certain time (the first light source is stopped at this time).
After repeating this for the required number of times, the modulation frequency is changed as necessary, and the same measurement is continued. Note that the above-mentioned fixed time can be appropriately selected according to the purpose, for example,
It is about 0.1 to 60 seconds, preferably about 1 to 10 seconds. The measurement time does not necessarily have to be the same for the first light source and the second light source. The modulation frequency is appropriately selected according to a desired measurement depth.
【００１１】光源から照射された光は、開放型のセルに
導かれる。先に示したように、１波長で測定すると、押
し当て方によって信号の強度が変化してしまう。そこで
本発明においては第一及び第二の光源から交互に入射さ
れる光を合波手段を介して重畳して単一のセルへと導
き、２波長で測定できるようにしている。この重畳は光
合波器を用いれば容易に行うことができる。光合波器か
らの光線は、例えば光ファイバによって、セルが当接さ
れる測定対象へと差し向けられる。セルの容積は必要以
上に大きいと感度が悪くなるので、デッドボリュームを
可能な限り低減することが望ましい。セルの好ましい容
積の範囲は0.01〜３cm3程度である。反射光に起因して
生ずるノイズを最小限に抑えるために、セルが遮光性材
料からなる外壁部と、この外壁部の内側に沿って設けら
れた低熱伝導率の光透過性材料からなる内壁部とを備え
ることが好ましい。Light emitted from the light source is guided to an open cell. As described above, when measuring at one wavelength, the intensity of the signal changes depending on the pressing method. Therefore, in the present invention, the light alternately incident from the first and second light sources is superimposed via a multiplexing means and led to a single cell so that measurement can be performed at two wavelengths. This superposition can be easily performed by using an optical multiplexer. The light beam from the optical multiplexer is directed, for example, by an optical fiber, to the measurement object to which the cell abuts. If the cell volume is unnecessarily large, the sensitivity is deteriorated. Therefore, it is desirable to reduce the dead volume as much as possible. A preferable range of the volume of the cell is about 0.01 to 3 cm 3 . In order to minimize noise caused by reflected light, the cell is made of an outer wall made of a light-shielding material, and an inner wall made of a light-transmitting material having a low thermal conductivity is provided along the inside of the outer wall. It is preferable to provide
【００１２】測定波長及び参照波長のそれぞれに応じて
対象物から生成される光音響信号は、時間領域において
検出される。これは例えば、音波として生成される光音
響信号をマイクロフォンのような圧電センサにより検出
することによって行われる。検出された信号は増幅後、
サンプリング、Ａ／Ｄ変換によって、信号処理手段へと
時系列データとして連続的に取り込むことができる。信
号処理手段は、第一及び第二の光源の駆動時間帯に関す
る信号、並びに変調周波数を参照信号として取り込んで
おり、これとの同期をとることによって、所定の時間領
域幅にわたって検出信号を積算、フーリエ変換し、被測
定物質及び対象物質に由来する光音響信号を周波数領域
において得る。フーリエ変換は、ＦＦＴ（高速フーリエ
変換）によって行うことが好ましい。A photoacoustic signal generated from an object according to each of the measurement wavelength and the reference wavelength is detected in a time domain. This is performed, for example, by detecting a photoacoustic signal generated as a sound wave by a piezoelectric sensor such as a microphone. After the detected signal is amplified,
By sampling and A / D conversion, the data can be continuously taken into the signal processing means as time-series data. The signal processing means takes in the signals relating to the drive time zones of the first and second light sources, and the modulation frequency as a reference signal, and by synchronizing with the reference signal, integrates the detection signal over a predetermined time domain width, Fourier transform is performed to obtain a photoacoustic signal derived from the substance to be measured and the target substance in the frequency domain. The Fourier transform is preferably performed by FFT (Fast Fourier Transform).
【００１３】本発明によれば、信号処理手段は光源を駆
動する変調信号から導出される光出力により、測定波長
及び参照波長に由来する光音響信号をそれぞれ強度補正
する。これは、光音響信号の強度が光源の出力に比例す
ることから、光源出力に起因する信号強度の相違を補正
するためである。強度補正された光音響信号は次いで、
参照波長で規格化される。即ち測定波長に対応する光音
響信号と、参照波長に対応する光音響信号の各々は、後
者を１として標準化され、測定対象に対する押圧力の相
違による影響を排除することができる。規格化された光
音響信号は差引され、これによってバックグラウンド信
号を除去し、被測定物質に由来する光音響信号を得るこ
とができる。本発明はこうした信号処理手法により、被
測定物質を高精度且つ高速に測定することを可能なもの
としている。According to the present invention, the signal processing means corrects the intensity of the photoacoustic signal derived from the measurement wavelength and the reference wavelength, respectively, based on the optical output derived from the modulation signal for driving the light source. This is to correct the difference in signal intensity due to the light source output since the intensity of the photoacoustic signal is proportional to the output of the light source. The intensity-corrected photoacoustic signal is then
It is standardized by the reference wavelength. That is, each of the photoacoustic signal corresponding to the measurement wavelength and the photoacoustic signal corresponding to the reference wavelength is standardized with the latter being 1, so that the influence of the difference in the pressing force on the measurement target can be eliminated. The standardized photoacoustic signal is subtracted, whereby the background signal is removed, and a photoacoustic signal derived from the substance to be measured can be obtained. The present invention makes it possible to measure a substance to be measured with high accuracy and high speed by using such a signal processing technique.
【００１４】本発明によれば、信号処理手段は、変調信
号の周波数及び被測定物質に由来する光音響信号の強度
及び位相に基づいて、対象物の表面から所定の深さにお
ける被測定物質の存在量を演算する演算手段を含むこと
ができる。即ち測定された光音響信号は、強度情報と共
に位相に関する情報をも含むことになるが、この位相は
光の照射から音波の検出までの時間遅れを表していると
考えられる。従って、位相角を小さくとれば対象物の表
面から浅いところからの情報が得られ、位相角を大きく
とれば対象物の表面から深いところからの情報が得られ
る。ここで任意の位相角ψにおいて得られる信号強度Ｙ
（ψ）は、最大信号強度Ｃが得られる位相角φに対し
て、Ｙ（ψ）＝Ｃcos（φ−ψ）の関係にある。熱拡散
率αを一定とすれば、信号強度がＹ（ψ）である測定深
さＤは、Ｄ＝［（π／４）＋ψ］×μによって近似的に
求めることができる。但しここにおいて、μは熱拡散長
であり、μ＝√（α／πｆ）（注：ｆは変調信号の周波
数）で表され、ψはＰＡＳの標準試料として用いられる
カーボンブラックの位相を基準としてとった任意の位相
角である。このように位相を用いて解析することによ
り、単一の変調周波数でもって、その単一の変調周波数
に由来する深さまでの対象物の深さ方向の分析が可能と
なる。もちろん、変調周波数を変化させて、測定可能な
深さ域を変え、深さ方向分析をそれぞれについて行うこ
ともできる。例えば対象物質が皮膚の場合、その熱拡散
率を７×10-4cm2／秒とすると、変調周波数が3000Hzで
あれば0.7〜４μmの深さを、また変調周波数が５Hzであ
れば20〜100μmの深さを測定できる。According to the present invention, the signal processing means determines whether or not the substance to be measured is at a predetermined depth from the surface of the object based on the frequency of the modulation signal and the intensity and phase of the photoacoustic signal derived from the substance to be measured. Operation means for calculating the abundance can be included. In other words, the measured photoacoustic signal includes information regarding the phase together with the intensity information, and this phase is considered to represent a time delay from the irradiation of light to the detection of the sound wave. Therefore, if the phase angle is small, information from a shallow position from the surface of the object can be obtained, and if the phase angle is large, information from a deep position from the surface of the object can be obtained. Here, the signal strength Y obtained at an arbitrary phase angle ψ
(Ψ) has a relationship of Y (ψ) = Ccos (φ−ψ) with respect to the phase angle φ at which the maximum signal strength C is obtained. Assuming that the thermal diffusivity α is constant, the measurement depth D at which the signal intensity is Y (ψ) can be approximately obtained by D = [(π / 4) + ψ] × μ. Here, μ is the thermal diffusion length and μ = √ (α / πf) (note: f is the frequency of the modulation signal), and ψ is based on the phase of carbon black used as a standard sample of PAS. Any phase angle taken. By performing analysis using the phase in this manner, it is possible to analyze the object in the depth direction with a single modulation frequency up to a depth derived from the single modulation frequency. Of course, it is also possible to change the modulation frequency, change the measurable depth range, and perform a depth direction analysis for each. For example, when the target substance is skin, assuming that the thermal diffusivity is 7 × 10 −4 cm 2 / sec, if the modulation frequency is 3000 Hz, the depth is 0.7 to 4 μm. A depth of 100 μm can be measured.
【００１５】[0015]
【発明の実施の形態】図１は本発明による光音響信号測
定装置の一実施例を示すブロック図である。光音響信号
測定装置10は、測定波長、例えば1480nmの光を照射する
半導体レーザー11と、参照波長、例えば1300nmの光を照
射する半導体レーザー12を光源として含む。これらの半
導体レーザー11及び12は、駆動手段13、例えば直流信号
が重畳された交流信号を変調信号として生成する変調装
置により、同一の変調周波数で交互に駆動される。半導
体レーザー11及び12から発せられるレーザー光は光合波
器14に導かれ、光ファイバー15を介してセル20に導かれ
る。FIG. 1 is a block diagram showing one embodiment of a photoacoustic signal measuring device according to the present invention. The photoacoustic signal measuring device 10 includes, as light sources, a semiconductor laser 11 that emits light having a measurement wavelength, for example, 1480 nm, and a semiconductor laser 12 that emits light having a reference wavelength, for example, 1300 nm. These semiconductor lasers 11 and 12 are alternately driven at the same modulation frequency by a driving unit 13, for example, a modulation device that generates an AC signal on which a DC signal is superimposed as a modulation signal. The laser light emitted from the semiconductor lasers 11 and 12 is guided to the optical multiplexer 14 and guided to the cell 20 via the optical fiber 15.
【００１６】図２はセル20の一例を詳細に示している。
セル20は被測定物質を含む対象物に押し当てられる開放
端部21を有し、開放端部21の周囲は遮光性材料からなる
外壁部22と、この外壁部22の内側に沿って設けられた低
熱伝導率の光透過性材料からなる内壁部23及び窓板26と
を備えている。光ファイバー15からセル20の開放端部21
に差し向けられたレーザー光は被測定物質を含む対象物
質に吸収され、音波を生成する。生成した音波はマイク
ロフォン24によって拾われ、プリアンプ25で増幅され
て、その後の処理のために逐次転送される。FIG. 2 shows an example of the cell 20 in detail.
The cell 20 has an open end 21 pressed against an object containing a substance to be measured, a periphery of the open end 21 is provided along an outer wall 22 made of a light-shielding material, and along the inside of the outer wall 22. And an inner wall portion 23 and a window plate 26 made of a light transmissive material having low thermal conductivity. Open end 21 of cell 20 from optical fiber 15
Is absorbed by the target substance including the substance to be measured, and generates a sound wave. The generated sound waves are picked up by the microphone 24, amplified by the preamplifier 25, and sequentially transferred for subsequent processing.
【００１７】再度図１を参照すると、セル20から得られ
る検出信号は、フィルタ16を介してサンプリングされ、
信号処理装置17へと送られる。この信号処理装置17は例
えばＦＦＴアナライザなどの周波数分析可能な装置であ
るが、デジタル化された時系列データをパソコンに連続
的に取り込み、周波数領域へとＦＦＴ変換するなどの手
段も可能である。変調信号との同期をとるために、信号
処理装置17は駆動手段13から変調信号を参照信号として
取り込んでいる。また、半導体レーザー11及び12の駆動
時間帯についての信号も入力されている。Referring again to FIG. 1, the detection signal obtained from cell 20 is sampled through filter 16 and
The signal is sent to the signal processing device 17. The signal processing device 17 is a device capable of performing frequency analysis such as an FFT analyzer. However, it is also possible to take digitalized time-series data continuously into a personal computer and perform FFT conversion into a frequency domain. In order to synchronize with the modulation signal, the signal processing device 17 takes in the modulation signal from the driving means 13 as a reference signal. Further, signals regarding the drive time zones of the semiconductor lasers 11 and 12 are also input.
【００１８】信号処理装置17は、参照信号から導出され
る光出力により、光音響信号を強度補正する。即ち測定
波長及び参照波長に対応して信号処理装置17において得
られた光音響信号をそれぞれQ'ｓ(ω)、Q'ｒ(ω)とすれ
ば、これらは光出力信号R'(ω)によって補正され、強度
補正信号A'ｓ(ω)＝Q'ｓ(ω)／R'(ω)、A'ｒ(ω)＝Q'ｒ
(ω)／R'(ω)が得られる。なおここでQ'ｓ（ω)＝Ｑｓ
（ω)ｅiφ(ω)、Q'ｒ（ω)＝Ｑｒ（ω)ｅiφ(ω)であ
り、Ｑ（ω)はＰＡＳ強度、φ（ω）は位相を示す。こ
れらはさらに規格化されて、B'ｓ(ω)＝A'ｓ(ω)／A'ｒ
(ω)、B'ｒ(ω)＝A'ｒ(ω)／A'ｒ(ω)となり、最終的に
被測定物質に由来する光音響信号がB'ｓ(ω)−B'ｒ(ω)
によって得られる。測定された光音響信号は、ＣＲＴ、
プリンタその他の適当な出力装置18へと送られて視覚化
される。The signal processing device 17 corrects the intensity of the photoacoustic signal based on the optical output derived from the reference signal. That is, assuming that the photoacoustic signals obtained in the signal processing device 17 corresponding to the measurement wavelength and the reference wavelength are Q's (ω) and Q'r (ω), these are the optical output signals R '(ω). A ′s (ω) = Q ′s (ω) / R ′ (ω), A′r (ω) = Q′r
(ω) / R ′ (ω) is obtained. Here, Q's (ω) = Qs
(Ω) e i φ ( ω ) , Q′r (ω) = Qr (ω) e i φ ( ω ) , where Q (ω) indicates PAS intensity and φ (ω) indicates phase. These are further standardized and B's (ω) = A's (ω) / A'r
(ω), B′r (ω) = A′r (ω) / A′r (ω), and the photoacoustic signal finally derived from the substance to be measured is B ′s (ω) −B′r ( ω)
Obtained by The measured photoacoustic signal is a CRT,
It is sent to a printer or other suitable output device 18 for visualization.
【００１９】本発明の別の実施例によれば、信号処理装
置17はさらに、被測定物質に由来する光音響信号の強度
及び位相に基づいて、対象物の表面から所定の深さにお
ける被測定物質の存在量を演算する処理部19を含む。こ
れは例えば先に述べたように、測定された光音響信号か
ら、任意の位相角ψに対応する成分を求めるものであ
る。この場合には、表面からある深さまでの光音響信号
強度を積分した形ではなしに、位相角ψにより示される
深さＤ（Ｄ＝［（π／４）＋ψ］×μ）における光音響
信号強度が得られる。従って位相角ψを変化させ、また
必要に応じて変調周波数を変化させることにより、対象
物の深さ方向の分析が可能となる。According to another embodiment of the present invention, the signal processing device 17 further includes a signal processing device 17 at a predetermined depth from the surface of the object based on the intensity and phase of the photoacoustic signal derived from the material to be measured. A processing unit 19 for calculating the amount of the substance is included. For example, as described above, a component corresponding to an arbitrary phase angle ψ is obtained from the measured photoacoustic signal. In this case, the photoacoustic signal at the depth D (D = [(π / 4) + ψ] × μ) indicated by the phase angle ψ is used instead of integrating the photoacoustic signal intensity from the surface to a certain depth. Strength is obtained. Therefore, by changing the phase angle ψ and, if necessary, the modulation frequency, it becomes possible to analyze the object in the depth direction.
【００２０】[0020]
実施例１ 人皮膚のアセトン／エーテル（Ａ／Ｅ）処理を行い、皮
膚の水分量の変化を測定した。使用した光音響信号測定
装置は図１の構成のものとし、測定用レーザーの波長は
1480nm、参照用レーザーの波長は1300nm、レーザー出力
はそれぞれ20mW、変調周波数は854Hzとした。測定用レ
ーザーと参照用レーザーは、6.5秒間ずつ交互に照射し
た。Example 1 Acetone / ether (A / E) treatment of human skin was performed, and changes in the water content of the skin were measured. The photoacoustic signal measuring device used has the configuration shown in FIG. 1, and the wavelength of the measuring laser is
The wavelength of the reference laser was 1300 nm, the laser output was 20 mW, and the modulation frequency was 854 Hz. The measurement laser and the reference laser were alternately irradiated for 6.5 seconds each.
【００２１】測定手順としては、人の前腕部を水洗いし
た後、20℃、湿度40％で20分間馴化した後にまず初期値
を測定した。その後15分間Ａ／Ｅ（１：１）処理し、５
分後、30分後及び60分後の値を測定した。また位相角と
して、−30゜、０゜、45゜及び90゜の４点をとったが、
皮膚の熱拡散長μを５μm（熱拡散率を７×10-4cm2/秒
とする。文献：K.Giese, K.Kolmel, J. Physique, coll
oque C6, 373 (1983)）とすると、変調周波数854Hzにお
いては、これらはそれぞれ皮膚の表面から１、４、８及
び12μmの深さに相当すると考えられる。得られた値を
初期値で規格化した結果を図３に示す。コントロールと
して、Ａ／Ｅ処理しない場合についての測定結果をやは
り図３に示す。図３から見られるように、全体的にＡ／
Ｅ処理によって水分量が減少し、その後回復するという
傾向が見られたが、表層ほど変化が大きく、内部は殆ど
変化していないことが判った。一般に、角質層内部は生
きた細胞である表皮部分に接しているため水分量が多く
て変化しにくいが、表層ほど環境の影響を受けやすいと
考えられているが、本発明の光音響信号測定装置によっ
て得られた結果はこうした知見と合致するものである。As a measurement procedure, after the forearm of a person was washed with water, it was conditioned at 20 ° C. and a humidity of 40% for 20 minutes, and then the initial value was measured. A / E (1: 1) treatment for 15 minutes thereafter, 5
After 30 minutes and 60 minutes, the values were measured. In addition, four points of -30 °, 0 °, 45 ° and 90 ° were taken as phase angles,
The thermal diffusion length μ of the skin is 5 μm (the thermal diffusivity is 7 × 10 −4 cm 2 / sec. References: K. Giese, K. Kolmel, J. Physique, coll
oque C6, 373 (1983)), at a modulation frequency of 854 Hz, these are considered to correspond to depths of 1, 4, 8, and 12 μm from the skin surface, respectively. FIG. 3 shows the result of normalizing the obtained values with the initial values. As a control, FIG. 3 also shows the measurement results when no A / E treatment was performed. As can be seen from FIG.
There was a tendency that the water content was reduced by the E treatment and then recovered, but it was found that the change was larger in the surface layer and the inside hardly changed. Generally, since the inside of the stratum corneum is in contact with the epidermis, which is a living cell, the amount of moisture is large and it is difficult to change, but it is thought that the surface layer is more susceptible to the environment, but the photoacoustic signal measurement of the present invention The results obtained with the instrument are consistent with these findings.
【００２２】実施例２ 人皮膚を活性剤で処理し、皮膚の水分量の変化を測定し
た。使用した光音響信号測定装置及び測定手法は実施例
１の場合と同様であるが、変調周波数は160Hzとした。Example 2 Human skin was treated with an active agent, and the change in the water content of the skin was measured. The photoacoustic signal measuring device and measuring method used were the same as those in Example 1, but the modulation frequency was 160 Hz.
【００２３】測定手順としては、実施例１の場合と同様
に、人の前腕部を水洗いした後、20℃、湿度40％で20分
間馴化した後にまず初期値を測定した。その後30分間サ
ンプル水溶液でカップシェイク処理し、10分後、30分後
及び60分後の値を測定した。この場合に位相角として
は、−30゜、０゜及び45゜の３点をとったが、この変調
周波数においては、これらはそれぞれ皮膚の表面から
３、10及び20μmの深さに相当すると考えられる。サン
プルとしては、５％ミリスチン酸カリウム塩、５％ＭＡ
Ｐセスキトリエタノールアミン塩及び水（コントロー
ル）を用いた。得られた値を初期値で規格化した結果を
図４に示す。図４から見られるように、ミリスチン酸塩
での処理によれば水分量が増大し、またＭＡＰ処理によ
れば水分量が減少し、その後回復するという傾向が見ら
れた。これは、ミリスチン酸塩はアルカリ性のため皮膚
を膨潤させ、これに対してＭＡＰは過乾燥を起こすとい
う知見に対応していると考えられる。As for the measurement procedure, as in the case of Example 1, the human forearm was washed with water, and after acclimatization at 20 ° C. and 40% humidity for 20 minutes, the initial value was measured first. Then, the sample was subjected to a cup shake treatment with a sample aqueous solution for 30 minutes, and the values after 10, 30, and 60 minutes were measured. In this case, three phase angles of -30 °, 0 ° and 45 ° were taken. At this modulation frequency, these correspond to depths of 3, 10 and 20 μm from the skin surface, respectively. Can be As a sample, 5% potassium myristic acid salt, 5% MA
P sesquitriethanolamine salt and water (control) were used. FIG. 4 shows the result of normalizing the obtained values with the initial values. As can be seen from FIG. 4, there was a tendency that the amount of water increased by the treatment with myristate, and the amount of water decreased by the MAP treatment, and then recovered. This is considered to correspond to the finding that myristate swells the skin due to alkalinity, whereas MAP causes overdrying.
【００２４】実施例３ 80℃で50時間硬化したフェノール樹脂と、同じ温度で77
時間硬化したフェノール樹脂について、樹脂中の水分量
を測定した。使用した光音響信号測定装置及び測定手
法、並びに変調周波数は実施例２の場合と同様である。
結果を図５に示す。硬化時間の増大に伴い、樹脂中の水
分量が減少することが示されている。Example 3 A phenol resin cured at 80 ° C. for 50 hours was mixed with a phenol resin at the same temperature for 77 hours.
The amount of water in the phenol resin cured for a time was measured. The used photoacoustic signal measuring device and measuring method, and the modulation frequency are the same as those in the second embodiment.
FIG. 5 shows the results. It is shown that as the curing time increases, the amount of water in the resin decreases.
【００２５】[0025]
【発明の効果】以上のように本発明によれば、皮膚の水
分量などをin vivo、in situで測定するに適した、開放
型のセルを有する光音響信号測定装置が提供される。こ
の装置は近赤外領域で好ましく動作し、光音響信号を高
精度且つ高速に測定することが可能である。また位相解
析を用いることにより、深さ方向の情報を、表面からの
足し合わせではなく、分離された形で得ることも可能と
なった。As described above, according to the present invention, there is provided a photoacoustic signal measuring apparatus having an open cell, which is suitable for measuring the water content of the skin in vivo and in situ. This device preferably operates in the near-infrared region, and is capable of measuring photoacoustic signals with high accuracy and high speed. Also, by using the phase analysis, it is possible to obtain information in the depth direction in a separated form, instead of adding the information from the surface.
【図１】本発明の光音響信号測定装置の一例を示すブロ
ック図である。FIG. 1 is a block diagram illustrating an example of a photoacoustic signal measurement device according to the present invention.
【図２】図１の装置に用いることのできるセルの一例を
示す部分断面立面図である。FIG. 2 is a partial cross-sectional elevation view showing an example of a cell that can be used in the apparatus of FIG.
【図３】人皮膚のＡ／Ｅ処理についての測定結果を示す
グラフである。FIG. 3 is a graph showing the measurement results for A / E treatment of human skin.
【図４】人皮膚の活性剤処理についての測定結果を示す
グラフである。FIG. 4 is a graph showing the measurement results for the treatment of human skin with an active agent.
【図５】フェノール樹脂中の水分量についての測定結果
を示すグラフである。FIG. 5 is a graph showing a measurement result of a water content in a phenol resin.
10 光音響信号測定装置 11,12 半導体レーザー 13 駆動手段 14 光合波器 15 光ファイバー 16 フィルタ 17 信号処理装置 18 出力装置 19 処理部 20 セル 21 開放端部 22 外壁部 23 内壁部 24 マイクロフォン 25 プリアンプ 26 窓板 10 Photoacoustic signal measuring device 11,12 Semiconductor laser 13 Driving means 14 Optical multiplexer 15 Optical fiber 16 Filter 17 Signal processing device 18 Output device 19 Processing unit 20 Cell 21 Open end 22 Outer wall 23 Inner wall 24 Microphone 25 Preamplifier 26 Window Board
───────────────────────────────────────────────────── フロントページの続き (72)発明者 奥田 峰広 栃木県芳賀郡市貝町赤羽2606 花王株式会 社研究所内 (72)発明者 澤田 嗣郎 東京都荒川区南千住６−37−２−504 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Minehiro Okuda 2606 Akabane, Kaiga-cho, Haga-gun, Tochigi Pref. Inside Kao Corporation Research Institute (72) Inventor Shiro Sawada 6-37-2-504 Minamisenju, Arakawa-ku, Tokyo
Claims (9)
光源手段と、 前記測定波長の光と前記参照波長の光を少なくとも１種
の変調信号でそれぞれ変調し、セルへと交互に導く１以
上の時間帯を有する変調手段と、 前記セルが開放端部を有し、前記測定波長の変調光と前
記参照波長の変調光を、合波手段を介して被測定物質を
含む対象物に差し向けることと、 前記測定波長及び参照波長のそれぞれに応じて対象物か
ら生成される光音響信号を時間領域において検出する検
出手段と、 前記変調手段と前記検出手段に接続され、前記変調手段
から導出される光出力により前記光音響信号を強度補正
し、強度補正された前記光音響信号を前記参照波長で規
格化し、規格化された前記光音響信号を差引し、前記被
測定物質に由来する光音響信号を周波数領域において得
る信号処理手段とからなる、光音響信号測定装置。1. A light source means for irradiating light of a measurement wavelength and light of a reference wavelength, and modulating the light of the measurement wavelength and the light of the reference wavelength with at least one type of modulation signal, and alternately guiding the light to the cell. Modulating means having one or more time zones, wherein the cell has an open end, and the modulated light of the measurement wavelength and the modulated light of the reference wavelength are converted to an object containing the substance to be measured via the multiplexing means. Directing, detecting means for detecting in the time domain a photoacoustic signal generated from the object in accordance with each of the measurement wavelength and the reference wavelength, and connected to the modulation means and the detection means, from the modulation means The photoacoustic signal is intensity-corrected by the derived light output, the intensity-corrected photoacoustic signal is normalized by the reference wavelength, the normalized photoacoustic signal is subtracted, and the photoacoustic signal is derived from the substance to be measured. Around the photoacoustic signal Comprising a signal processing means for obtaining the number region, the photoacoustic signal measurement device.
第一の光源と参照波長の光を照射する第二の光源を少な
くとも有し、前記変調手段が前記第一の光源及び前記第
二の光源を前記少なくとも１種の変調信号で交互に駆動
する１以上の時間帯を有する駆動手段を含む、請求項１
の光音響信号測定装置。2. The light source means has at least a first light source for irradiating light of a measurement wavelength and a second light source for irradiating light of a reference wavelength, and the modulating means has the first light source and the second light source. And driving means having at least one time slot for alternately driving the light sources with the at least one type of modulation signal.
Photoacoustic signal measuring device.
ある、請求項２の光音響信号測定装置。3. The photoacoustic signal measuring device according to claim 2, wherein said first and second light sources are laser light sources.
請求項３の光音響信号測定装置。4. The laser light source is a semiconductor laser.
The photoacoustic signal measuring device according to claim 3.
々において、前記測定波長の光と前記参照波長の光につ
いて同一である、請求項１から４の何れか１の光音響信
号測定装置。5. The photoacoustic signal measuring device according to claim 1, wherein the modulated signal is the same for the light of the measurement wavelength and the light of the reference wavelength in each of the one or more time zones. .
と、該外壁部の内側に沿って設けられた低熱伝導率の光
透過性材料からなる内壁部とを備える、請求項１から５
の何れか１の光音響信号測定装置。6. The cell according to claim 1, wherein the cell includes an outer wall portion made of a light-shielding material, and an inner wall portion made of a light-transmitting material having a low thermal conductivity provided along the inside of the outer wall portion.
Any one of the photoacoustic signal measuring devices.
リングする手段を含み、前記信号処理手段がＦＦＴ手段
を含む、請求項１から６の何れか１の光音響信号測定装
置。7. The photoacoustic signal measuring device according to claim 1, wherein said detecting means includes means for sampling said photoacoustic signal, and said signal processing means includes FFT means.
由来する光音響信号の強度及び位相に基づいて、前記対
象物の表面から所定の深さにおける前記被測定物質の存
在量を演算する演算手段を含む、請求項１から７の何れ
か１の光音響信号測定装置。8. The signal processing means calculates the amount of the substance to be measured at a predetermined depth from the surface of the object based on the intensity and phase of the photoacoustic signal derived from the substance to be measured. The photoacoustic signal measurement device according to any one of claims 1 to 7, further comprising a calculation unit.
長が水に特異的に吸収される近赤外波長である、請求項
１から８の何れか１の光音響信号測定装置。9. The photoacoustic signal measurement device according to claim 1, wherein the substance to be measured is water, and the measurement wavelength is a near infrared wavelength that is specifically absorbed by water.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32136396A JP3500259B2 (en) | 1996-12-02 | 1996-12-02 | Photoacoustic signal measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32136396A JP3500259B2 (en) | 1996-12-02 | 1996-12-02 | Photoacoustic signal measuring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10160711A true JPH10160711A (en) | 1998-06-19 |
| JP3500259B2 JP3500259B2 (en) | 2004-02-23 |
Family
ID=18131741
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP32136396A Expired - Fee Related JP3500259B2 (en) | 1996-12-02 | 1996-12-02 | Photoacoustic signal measuring device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3500259B2 (en) |
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