JP2923779B1 - Optical interference device for ultrasonic detection - Google Patents
Optical interference device for ultrasonic detectionInfo
- Publication number
- JP2923779B1 JP2923779B1 JP10171662A JP17166298A JP2923779B1 JP 2923779 B1 JP2923779 B1 JP 2923779B1 JP 10171662 A JP10171662 A JP 10171662A JP 17166298 A JP17166298 A JP 17166298A JP 2923779 B1 JP2923779 B1 JP 2923779B1
- Authority
- JP
- Japan
- Prior art keywords
- light
- optical
- intensity
- interferometer
- semi
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Landscapes
- Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
【要約】
【課題】被測定物の超音波振動を光を用いて検出する超
音波検出用光干渉方法を提供する。
【解決手段】相対向する一対の半透過凹面鏡５の間に挿
入した両凸レンズ３によりにより光干渉計を構成し、上
記半透過凹面鏡５で直接反射した光と、上記光干渉計か
らの出力光を逆位相で干渉させて強度が０に近い干渉光
をつくり、干渉光を干渉光強度信号と外部参照信号との
位相差を測定して超音波振動による光周波数の変化を検
出する。An optical interference method for ultrasonic detection that detects ultrasonic vibration of an object to be measured using light is provided. An optical interferometer is constituted by a biconvex lens (3) inserted between a pair of opposing semi-transmissive concave mirrors (5), and light directly reflected by the semi-transmissive concave mirror (5) and output light from the optical interferometer (5). Are made to interfere with each other in opposite phases to produce interference light having an intensity close to 0, and the interference light is measured for the phase difference between the interference light intensity signal and the external reference signal to detect a change in the optical frequency due to ultrasonic vibration.
Description
【０００１】[0001]
【発明の属する技術分野】本発明は非接触の超音波非破
壊検査において、特に高輝度光源を用いて超音波による
振動を光の周波数変化として検出する装置に関するもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact non-destructive ultrasonic inspection, and more particularly to an apparatus for detecting vibrations caused by ultrasonic waves as a change in the frequency of light using a high-intensity light source.
【０００２】[0002]
【従来の技術】従来の超音波検出のための光干渉計にお
いては、図５に示すように２枚の対向する半透過凹面鏡
５，５を、その曲率半径Ｆ０（焦点距離はＦ０／２）の
距離だけ離して対面させた共焦点ファブリペロー光干渉
計が使用されてきた。2. Description of the Related Art In a conventional optical interferometer for detecting an ultrasonic wave, as shown in FIG. 5, two opposing semi-transparent concave mirrors 5 and 5 are provided with a radius of curvature F0 (focal length is F0 / 2). Confocal Fabry-Perot optical interferometers facing each other have been used.
【０００３】共焦点ファブリペロー光干渉計による測定
では、光源１からの光を超音波振動している被測定物２
で反射させ、反射光をレンズ３、ビームスプリッタ４を
通して干渉計に導き、干渉計からの反射光を光検出器７
で検出して、超音波のドップラーシフト効果による光周
波数の変化を測定する。干渉計からの反射光には図６に
示すように３つの成分がある。第１に入力側の半透過鏡
で直接反射された光Ｅｒｅｆ、第２に光干渉計内部で４
ｎ＋３回（ｎ≧０の整数）反射されて出力される光Ｅ
１、第３に干渉計内部で４ｎ＋１回反射された光Ｅ２で
ある。In the measurement by the confocal Fabry-Perot optical interferometer, the light from a light source 1
And the reflected light is guided to the interferometer through the lens 3 and the beam splitter 4, and the reflected light from the interferometer is detected by the photodetector 7.
And the change of the optical frequency due to the Doppler shift effect of the ultrasonic wave is measured. The reflected light from the interferometer has three components as shown in FIG. First, the light Eref directly reflected by the input side semi-transmissive mirror, and secondly, the light Eref 4 inside the optical interferometer.
Light E reflected and output n + 3 times (n ≧ 0)
First and third, light E2 reflected 4n + 1 times inside the interferometer.
【０００４】一般に、入力される光ビームの径は大き
く、これら３成分を空間的に分離するのは困難であるた
め、すべて成分は光検出器で検出される。共焦点鏡の使
用により、粗面から反射された散乱光であっても自動的
に光Ｅ１は光Ｅｒｅｆと重なるため、鏡面でない被測定
物においても光干渉測定が可能であることが最大の特徴
である。In general, the diameter of an input light beam is large, and it is difficult to spatially separate these three components. Therefore, all components are detected by a photodetector. By using the confocal mirror, even if the scattered light is reflected from the rough surface, the light E1 automatically overlaps with the light Eref. It is.
【０００５】しかし、同時に発生する光Ｅ２は、Ｅｒｅ
ｆやＥ１とは空間的に干渉性を持たず、干渉に寄与しな
い。鏡の間隔Ｌ若しくは光周波数νにたいして、光検出
器により得られる干渉光強度信号は図７に示される周期
信号となる。このとき、光干渉に寄与しないＥ２成分の
存在により、干渉光強度の最小値はゼロにならず、最大
強度値の半分にとどまる。However, the light E2 generated at the same time is
f and E1 have no spatial coherence and do not contribute to interference. The interference light intensity signal obtained by the photodetector for the mirror interval L or the optical frequency ν is a periodic signal shown in FIG. At this time, due to the existence of the E2 component that does not contribute to the optical interference, the minimum value of the interference light intensity does not become zero but remains half of the maximum intensity value.
【０００６】被測定物より反射される光の周波数は、被
測定物の超音波振動にともなうドップラー効果によりΔ
ｆだけ変調される。この周波数変化は図７に示されるよ
うに、干渉光強度信号の振幅変化となり、信号の交流成
分を抽出することにより超音波振動を測定することがで
きる。The frequency of the light reflected from the object to be measured is ΔΔ due to the Doppler effect accompanying the ultrasonic vibration of the object to be measured.
It is modulated by f. This frequency change, as shown in FIG. 7, results in a change in the amplitude of the interference light intensity signal, and the ultrasonic vibration can be measured by extracting the AC component of the signal.
【０００７】超音波による光周波数の変化を最大の検出
感度で検出するため、干渉光強度信号を図５の信号増幅
器８で増幅して制御回路９を駆動し、図７のＡ点に干渉
光強度を維持するよう干渉計の鏡の間隔Ｌを圧電素子６
により制御する。In order to detect the change in the optical frequency due to the ultrasonic wave with the maximum detection sensitivity, the interference light intensity signal is amplified by the signal amplifier 8 in FIG. 5 and the control circuit 9 is driven. To maintain the strength, the distance L between the mirrors of the interferometer is
Is controlled by
【０００８】共焦点ファブリペロー光干渉計による超音
波の検出は、測定対象表面の性状に影響を受けにくく、
また低周波の機械的な外乱振動に対して干渉光強度信号
は影響されない。さらに、信号雑音比は光干渉計への入
力光強度の平方根に比例するため、高輝度の光源を使用
することが感度の向上につながる。（Ｂｒｏａｄｂａｎ
ｄ ｏｐｔｉｃａｌ ｄｅｔｅｃｔｉｏｎ ｏｆ ｕｌ
ｔｒａｓｏｕｎｄ ｂｙ ｏｐｔｉｃａｌ ｓｉｄｅｂ
ａｎｄ ｓｔｒｉｐｐｉｎｇ ｗｉｔｈ ａ ｃｏｎｆ
ｏｃａｌ Ｆａｂｒｙ−Ｐｅｒｏｔ：Ａｐｐｌ． Ｐｈ
ｙｓ． Ｌｅｔｔ． ｖｏｌ．５５ ｐ．１６１２
（１９８９） ）The detection of ultrasonic waves by a confocal Fabry-Perot optical interferometer is hardly affected by the properties of the surface to be measured.
Also, the interference light intensity signal is not affected by low-frequency mechanical disturbance vibration. Furthermore, since the signal-to-noise ratio is proportional to the square root of the input light intensity to the optical interferometer, using a light source with high brightness leads to an improvement in sensitivity. (Broadban
d optical detection of ul
trasound by optical sideb
and stripping with a conf
ocal Fabry-Perot: Appl. Ph
ys. Lett. vol. 55 p. 1612
(1989))
【０００９】[0009]
【発明が解決しようとする課題】しかし、上記従来の光
干渉装置においては、信号検出の感度を向上させるた
め、入力光の強度を大きくすると、必然的に光検出器に
入力される光量が大きくなる。そのため、光検出器が飽
和して線形性を失った領域では、微小な干渉光強度変化
に対して感度が悪くなり、光検出器の線形領域によっ
て、使用できる光源の強度が制限される重大な課題があ
った。さらに、光源の強度変化によっても、干渉光強度
が変化するため、超音波振動による光周波数の変化成分
と、光源の強度の変化成分が検出信号に混在して出力さ
れる問題点があった。However, in the above-mentioned conventional optical interference device, if the intensity of the input light is increased in order to improve the sensitivity of signal detection, the amount of light input to the photodetector inevitably increases. Become. Therefore, in a region where the photodetector is saturated and loses linearity, sensitivity to a small change in the intensity of the interference light is deteriorated, and the linear region of the photodetector limits the intensity of a light source that can be used. There were challenges. Further, since the interference light intensity also changes due to the intensity change of the light source, there is a problem that the change component of the optical frequency due to the ultrasonic vibration and the change component of the intensity of the light source are mixed and output in the detection signal.
【００１０】[0010]
【課題を解決するための手段】そこで、上記課題を解決
するため、本発明は、一対の相対向する半透過凹面鏡
と、該２つの半透過凹面鏡の中間に挿入した両凸レンズ
により光干渉計を構成し、外部信号により位相変調した
高輝度光を光干渉計に入力し、入力側の半透過凹面鏡で
直接反射された光と、光干渉計内部で多重反射して干渉
計から出力された光を逆位相で干渉させ、光強度がゼロ
に近い干渉光を光検出器で検出した後、この干渉光強度
信号と上記外部信号との位相差を測定することにより、
高輝度光を使用して光検出器を飽和させることなく、超
音波のドップラーシフト効果による光周波数の変化成分
を出力する超音波検出用光干渉装置を提供する。In order to solve the above-mentioned problems, the present invention provides an optical interferometer comprising a pair of opposed semi-transmissive concave mirrors and a biconvex lens inserted between the two semi-transparent concave mirrors. High-brightness light phase-modulated by an external signal is input to the optical interferometer, and the light directly reflected by the semi-transmissive concave mirror on the input side and the light output from the interferometer after multiple reflection inside the optical interferometer By interfering in the opposite phase, the light intensity is detected by the photodetector interference light near zero, by measuring the phase difference between this interference light intensity signal and the external signal,
Provided is an optical interference device for ultrasonic detection that outputs a change component of an optical frequency due to a Doppler shift effect of an ultrasonic wave without using a high-intensity light to saturate a photodetector.
【００１１】[0011]
【発明の実施の形態】以下、本発明の実施形態について
図面を参照して説明する。図１は本発明の第１の実施形
態を示す概略構成図であって、光源１、被測定物２、両
凸レンズ３、ビームスプリッタ４、一対の半透過凹面鏡
５、圧電素子６、光検出器７、信号増幅器８、制御回路
９、発振器１０、光位相変調器１１、位相シフタ１２、
ミキサー１３、両凸レンズ１４により構成されている。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, in which a light source 1, a device under test 2, a biconvex lens 3, a beam splitter 4, a pair of semi-transmissive concave mirrors 5, a piezoelectric element 6, a photodetector 7, signal amplifier 8, control circuit 9, oscillator 10, optical phase modulator 11, phase shifter 12,
It comprises a mixer 13 and a biconvex lens 14.
【００１２】光源１は干渉性の高い連続発振レーザを使
用する。光源１からの光を光位相変調器１１で超音波周
波数より高い周波数ｆｍで変調し、被測定物からの反射
光を光干渉計に導く。一対の半透過凹面鏡５の間隔を２
Ｆ０とし、鏡の中間点に焦点距離Ｆ０／２の両凸レンズ
１４を置く。これにより、一対の半透過凹面鏡５と両凸
レンズ１４との焦点が重なる。この際の光干渉計と多重
反射光の関係を図２に示す。The light source 1 uses a continuous wave laser having high coherence. The light from the light source 1 is modulated by the optical phase modulator 11 at a frequency fm higher than the ultrasonic frequency, and the reflected light from the object to be measured is guided to the optical interferometer. The distance between the pair of semi-transmissive concave mirrors 5 is 2
F0 is set, and a biconvex lens 14 having a focal length of F0 / 2 is placed at an intermediate point of the mirror. Thereby, the focal points of the pair of semi-transmissive concave mirrors 5 and the biconvex lens 14 overlap. FIG. 2 shows the relationship between the optical interferometer and the multiple reflected light at this time.
【００１３】半透過凹面鏡５を構成する鏡面で直接反射
した光Ｅｒｅｆと干渉計内部で反射した光Ｅ３は干渉す
るため、散乱光を干渉させる特徴は保持したままであ
る。一方、従来の共焦点ファブリペロー干渉計で発生す
るＥ２成分がないため、干渉光強度の最小値はほとんど
ゼロとなる。光検出器７で得られる干渉光強度信号はｆ
ｍの周波数成分を持ち、この信号と発振器１０からの変
調信号をミキサー１３で位相検出して両者の位相差に対
応する直流信号を作る。Since the light Eref directly reflected by the mirror surface constituting the semi-transmissive concave mirror 5 and the light E3 reflected inside the interferometer interfere with each other, the feature of causing the scattered light to interfere is maintained. On the other hand, since there is no E2 component generated by the conventional confocal Fabry-Perot interferometer, the minimum value of the interference light intensity is almost zero. The interference light intensity signal obtained by the photodetector 7 is f
The phase of this signal and the modulation signal from the oscillator 10 are detected by the mixer 13 to produce a DC signal corresponding to the phase difference between the two.
【００１４】ここで、直流信号への変換効率が最大にな
るよう位相シフタ１２を調整する。間隔Ｌ、若しくは光
周波数νの変化に対して光検出器による干渉光強度信号
は図３（ａ）に示す周期信号となり、このとき位相差信
号は図３（ｂ）となる。Here, the phase shifter 12 is adjusted so that the conversion efficiency into a DC signal is maximized. The interference light intensity signal by the photodetector becomes a periodic signal shown in FIG. 3A with respect to the change of the interval L or the optical frequency ν, and the phase difference signal becomes that shown in FIG. 3B.
【００１５】この位相差信号により圧電素子６を制御回
路９を介して駆動し、鏡の間隔を制御して図３（ｂ）の
Ｂ点を作動点とする。これにより、干渉光の強度がほと
んどゼロであるダークフリンジに作動点が固定される。
超音波振動によるドップラーシフトにより、位相差信号
の振幅は図３（ｂ）に示されるように変化する。また、
光源の光強度の変化は、位相差信号に影響しないため、
光周波数の変化成分だけが忠実に検出できる。The piezoelectric element 6 is driven by the phase difference signal via the control circuit 9 to control the distance between the mirrors, and the point B in FIG. 3B is set as the operating point. Thus, the operating point is fixed to the dark fringe where the intensity of the interference light is almost zero.
Due to the Doppler shift due to the ultrasonic vibration, the amplitude of the phase difference signal changes as shown in FIG. Also,
Since the change in light intensity of the light source does not affect the phase difference signal,
Only the change component of the optical frequency can be accurately detected.
【００１６】本発明の第２の実施形態においては、第１
の実施形態で示した光源１の連続レーザ光を光増幅器１
６によりパルス的に光増幅し、大出力パルス光を被測定
物２に照射する。被測定物からのパルス反射光を第１の
実施形態と同様に光干渉計に入力する。同時に、光干渉
計をダークフリンジに固定するため、増幅前の連続光も
ビームサンプラー１５と鏡１７により光干渉計に入力す
る。そして、大出力の光を使用することにより、測定の
感度を向上させる。また、ダークフリンジが作動点であ
るため、入力光のパルス的な光量の増加は、検出信号に
影響を与えない。In a second embodiment of the present invention, the first
The continuous laser light of the light source 1 shown in the embodiment
The light is pulse-amplified by 6 and a large output pulse light is irradiated to the device under test 2. The pulse reflected light from the object to be measured is input to the optical interferometer as in the first embodiment. At the same time, the continuous light before amplification is also input to the optical interferometer by the beam sampler 15 and the mirror 17 in order to fix the optical interferometer to the dark fringe. Then, the sensitivity of the measurement is improved by using the high output light. Further, since the dark fringe is the operating point, an increase in the pulsed light amount of the input light does not affect the detection signal.
【００１７】なお、本発明によれば、光が干渉して打ち
消し合ったダークフリンジで検出を行うため、高輝度の
光源の使用においても光検出器は飽和することなく、さ
らに光源の強度変化に影響されず光周波数の変化だけを
検出する光干渉計として作用する。According to the present invention, since the detection is performed with the dark fringes that cancel each other out due to the interference of light, the light detector does not saturate even when a high-intensity light source is used, and furthermore, the intensity of the light source does not change. It acts as an optical interferometer that detects only changes in optical frequency without being affected.
【００１８】以上、本発明を図面に記載された実施形態
に基づいて説明したが、本発明は上記した実施形態だけ
ではなく、特許請求の範囲に記載した構成を変更しない
限りどのようにでも実施することができる。As described above, the present invention has been described based on the embodiments described in the drawings. However, the present invention is not limited to the above-described embodiments, but may be implemented in any manner unless the configuration described in the claims is changed. can do.
【００１９】[0019]
【発明の効果】本発明によれば、従来不可能であったフ
ァブリペロー光干渉計による高輝度光源を利用した信号
感度の向上が可能であり、また、光源の強度の変動に影
響されにくい超音波振動信号の検出が実現できる。According to the present invention, it is possible to improve the signal sensitivity using a high-intensity light source by a Fabry-Perot optical interferometer, which has been impossible in the past, and to obtain an ultra-sensitive device which is hardly affected by variations in the intensity of the light source. Detection of a sound wave vibration signal can be realized.
【図１】本発明の第１の実施形態にかかる装置の構成を
示すブロック図である。FIG. 1 is a block diagram illustrating a configuration of an apparatus according to a first embodiment of the present invention.
【図２】本発明に係る光干渉計と干渉する光の成分を示
す概念図である。FIG. 2 is a conceptual diagram showing light components that interfere with the optical interferometer according to the present invention.
【図３】本発明に係る光干渉計の作動原理を説明する概
念図である。FIG. 3 is a conceptual diagram illustrating the operation principle of the optical interferometer according to the present invention.
【図４】本発明の第２の実施形態にかかる装置の構成を
示すブロック図である。FIG. 4 is a block diagram illustrating a configuration of an apparatus according to a second embodiment of the present invention.
【図５】従来のファブリペロー光干渉計の構成を示すブ
ロック図である。FIG. 5 is a block diagram showing a configuration of a conventional Fabry-Perot optical interferometer.
【図６】従来のファブリペロー光干渉計の作動原理を説
明する概念図である。FIG. 6 is a conceptual diagram illustrating the operation principle of a conventional Fabry-Perot optical interferometer.
【図７】従来のファブリペロー光干渉計と干渉する光の
成分を示す概念図である。FIG. 7 is a conceptual diagram showing light components that interfere with a conventional Fabry-Perot optical interferometer.
１ 光源 ２ 被測定物 ３，１４ 両凸レンズ ４ ビームスプリッタ ５ 半透過凹面鏡 ６ 圧電素子 ７ 光検出器 ８ 信号増幅器 ９ 制御回路 １０ 発振器 １１ 光位相変調器 １２ 位相シフタ １３ ミキサー １５ ビームサンプラー １６ 光増幅器 １７ 鏡 Reference Signs List 1 light source 2 device under test 3, 14 biconvex lens 4 beam splitter 5 semi-transmissive concave mirror 6 piezoelectric element 7 photodetector 8 signal amplifier 9 control circuit 10 oscillator 11 optical phase modulator 12 phase shifter 13 mixer 15 beam sampler 16 optical amplifier 17 mirror
Claims (1)
つの半透過凹面鏡の中間に挿入した両凸レンズにより光
干渉計を構成し、外部信号により位相変調した高輝度光
を光干渉計に入力し、入力側の半透過凹面鏡で直接反射
された光と、光干渉計内部で多重反射して干渉計から出
力された光を逆位相で干渉させ、光強度がゼロに近い干
渉光を光検出器で検出した後、この干渉光強度信号と上
記外部信号との位相差を測定することにより、高輝度光
を使用して光検出器を飽和させることなく、超音波のド
ップラーシフト効果による光周波数の変化成分を出力す
ることを特徴とする超音波検出用光干渉装置。A pair of opposing semi-transparent concave mirrors;
An optical interferometer is formed by a biconvex lens inserted between the two semi-transmissive concave mirrors, high-intensity light phase-modulated by an external signal is input to the optical interferometer, and light directly reflected by the input-side semi-transmissive concave mirror, The light output from the interferometer due to multiple reflection inside the optical interferometer is caused to interfere in antiphase, and the interference light having a light intensity close to zero is detected by the photodetector. Measuring the phase difference of the light, and outputting a change component of the optical frequency due to the Doppler shift effect of the ultrasonic wave without using the high-intensity light to saturate the photodetector. Interference device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10171662A JP2923779B1 (en) | 1998-06-18 | 1998-06-18 | Optical interference device for ultrasonic detection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10171662A JP2923779B1 (en) | 1998-06-18 | 1998-06-18 | Optical interference device for ultrasonic detection |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2923779B1 true JP2923779B1 (en) | 1999-07-26 |
| JP2000002690A JP2000002690A (en) | 2000-01-07 |
Family
ID=15927381
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10171662A Expired - Lifetime JP2923779B1 (en) | 1998-06-18 | 1998-06-18 | Optical interference device for ultrasonic detection |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2923779B1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10054676B2 (en) * | 2012-05-03 | 2018-08-21 | Los Alamos National Security, Llc | Acoustic camera |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2000122785A (en) | 1998-10-20 | 2000-04-28 | Fujitsu Ltd | Www server and recording medium |
| EP2363685B1 (en) * | 2010-02-09 | 2013-11-20 | Attocube Systems AG | Positioning device with confocal Fabry-Perot interferometer |
| KR101220602B1 (en) | 2010-12-28 | 2013-01-10 | 니뽄스틸코포레이션 | ultrasound measuring apparatus and method |
-
1998
- 1998-06-18 JP JP10171662A patent/JP2923779B1/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10054676B2 (en) * | 2012-05-03 | 2018-08-21 | Los Alamos National Security, Llc | Acoustic camera |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2000002690A (en) | 2000-01-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5827971A (en) | Optical vibration detection spectral analysis assembly and method for detecting vibration in an object of interest | |
| JPH07311182A (en) | Evaluation of sample by measurement of thermo-optical displacement | |
| JPH0216419A (en) | Optical detection method and apparatus for transient motion from scattering surface | |
| JP2923779B1 (en) | Optical interference device for ultrasonic detection | |
| JP2004226093A (en) | Laser vibrometer | |
| JP3029757B2 (en) | Sample evaluation method by photothermal displacement measurement | |
| JPH06186337A (en) | Laser distance measuring equipment | |
| JP3150239B2 (en) | Measuring device for micro-periodic vibration displacement | |
| Jang et al. | Non-contact detection of laser-generated surface acoustic waves using fiber optic Sagnac interferometer | |
| JPS6371675A (en) | Laser distance measuring instrument | |
| JPH09133585A (en) | Optical pulse train measuring method | |
| JP3000729B2 (en) | Photoacoustic signal detection method and device therefor | |
| JP2735348B2 (en) | Sample evaluation method with a single light source using thermal expansion vibration | |
| JPH0921752A (en) | Method for measuring photothermal displacement | |
| KR100588532B1 (en) | Apparatus of laser-ultrasonics measurement using reflective photo detector | |
| JPH05288720A (en) | Evaluating method of sample by ultrasonic vibration measurement | |
| JPS60224044A (en) | Surface inspecting device by light heterodyne interference method | |
| JPS6275363A (en) | Laser distance measuring apparatus | |
| JPH10170334A (en) | Vibration measuring instrument | |
| JPH07286993A (en) | Laser ultrasonic construction material measurement device | |
| JP2002005748A (en) | Light wavelength measuring device | |
| JPH07159114A (en) | Microdisplacement gage | |
| JPH05288721A (en) | Evaluating method of sample by photothermal displacement measurement | |
| JPH05264516A (en) | Noncontact detection method and device for ultrasonic wave | |
| Nakano et al. | Optical detection of ultrasound with a phase-modulated Michelson interferometer |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| EXPY | Cancellation because of completion of term |