JPH06186208A - Method of generating elastic waves - Google Patents
Method of generating elastic wavesInfo
- Publication number
- JPH06186208A JPH06186208A JP4355522A JP35552292A JPH06186208A JP H06186208 A JPH06186208 A JP H06186208A JP 4355522 A JP4355522 A JP 4355522A JP 35552292 A JP35552292 A JP 35552292A JP H06186208 A JPH06186208 A JP H06186208A
- Authority
- JP
- Japan
- Prior art keywords
- elastic wave
- subject
- elastic
- laser
- interference fringes
- 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
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- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は、材料評価法、非破壊
検査法等において使用する弾性波の発生方法に関するも
のである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of generating elastic waves used in material evaluation methods, nondestructive inspection methods and the like.
【０００２】[0002]
【従来の技術】材料や構造物の内部を弾性波で非破壊的
に検査する場合の超音波検査法は超音波を被検体に送り
込んで、そのエコーを使って被検体の内部の状態を検査
している。この超音波を発生させる方法としては、従来
ではバルク波放射の圧電素子を被検体に取り付けて使用
するのが主体である。しかし、被検体が移動しているも
のであったり、或いは被検体が高温のものであったりす
るなど、被検体の状態によっては、被検体の表面に圧電
素子を接触させることが適当でない場合もあり、接触方
式は使用環境や接触媒体の影響による精度低下など問題
点がある。したがって、非接触で被検体に超音波を送り
込むことができれば、測定環境に対する制約がなくな
る。このようなことから、レーザーを用いて弾性波を発
生させ、この弾性波を被検体に非接触で送り込む方法が
従来、提案されている。従来提案されているレーザーを
用いて非接触で弾性波を発生させる技術としては、レー
ザー超音波法、単一ビーム走査法、光ファイバーフェー
ズドアレイ法などがある。2. Description of the Related Art An ultrasonic inspection method for nondestructively inspecting the inside of a material or a structure with elastic waves sends ultrasonic waves to an object and inspects the internal state of the object using the echo. is doing. As a method of generating this ultrasonic wave, conventionally, a bulk wave radiating piezoelectric element is mainly attached to a subject and used. However, depending on the state of the subject, such as when the subject is moving or the subject has a high temperature, it may not be appropriate to bring the piezoelectric element into contact with the surface of the subject. However, the contact method has problems such as a decrease in accuracy due to the influence of the operating environment and the contact medium. Therefore, if the ultrasonic waves can be sent to the subject without contact, there are no restrictions on the measurement environment. For this reason, conventionally, a method has been proposed in which an elastic wave is generated using a laser and the elastic wave is sent to a subject without contact. Conventionally proposed techniques for non-contact generation of elastic waves using a laser include a laser ultrasonic method, a single beam scanning method, and an optical fiber phased array method.
【０００３】[0003]
【発明が解決しようとする課題】しかるに、このうち、
レーザー超音波法は、パルスレーザ等のビームを物体に
照射して超音波を発生させる方法であって、物体に非接
触で遠隔から走査できるという大きな特長をもつが、ビ
ームのパワー密度が大きいと物体が損傷するため十分大
きい振幅がとれないこと、および指向性が制御できない
ことなど、従来の圧電素子を用いる方法に及ばない点も
多い。[Problems to be Solved by the Invention]
The laser ultrasonic method is a method of irradiating an object with a beam such as a pulsed laser to generate ultrasonic waves, and has the great advantage that it can be remotely scanned without contacting the object, but if the power density of the beam is large There are many points inferior to the conventional method using a piezoelectric element, such as the fact that a sufficiently large amplitude cannot be obtained because the object is damaged and the directivity cannot be controlled.
【０００４】単一ビーム走査法は、単一のレーザービー
ムを走査する方法であって、弾性表面波及びバルク弾性
波を効率良く発生できるが、高周波化は困難である。そ
の理由は高速走査と鋭い集束の条件が、周波数５０ＭＨ
ｚより高い周波数に対しては同時には満足されないから
である。The single beam scanning method is a method of scanning a single laser beam, and can efficiently generate surface acoustic waves and bulk acoustic waves, but it is difficult to increase the frequency. The reason is that the condition of high-speed scanning and sharp focusing is that the frequency is 50 MHz.
This is because the frequencies higher than z cannot be satisfied at the same time.
【０００５】光ファイバーフェーズドアレイ法は、光フ
ァイバーアレイを用いるものであって、指向性の良いバ
ルク弾性波を発生できるが、放射方向は周波数を決める
とファイバーの長さの差によって一義的に決まってしま
って自由度はない。The optical fiber phased array method uses an optical fiber array and can generate bulk acoustic waves with good directivity, but the radiation direction is uniquely determined by the difference in fiber length when the frequency is determined. There is no freedom.
【０００６】この発明は、上記の如き事情に鑑みてなさ
れたものであって、大振幅の弾性波の発生を実現するこ
とができ、また、弾性波の放射方向の制御が可能であ
り、かつ、被検体に損傷を与えることがない弾性波の発
生方法を提供することを目的とするものである。The present invention has been made in view of the above circumstances and is capable of realizing the generation of a large amplitude elastic wave, and is also capable of controlling the emission direction of the elastic wave, and An object of the present invention is to provide a method of generating elastic waves that does not damage the subject.
【０００７】[0007]
【課題を解決するための手段】この目的に対応して、こ
の発明の弾性波の発生方法は、２本の周波数のわずかに
異なる干渉性エネルギービームを被検体上で交差させて
照射して、走査される干渉縞を生成し、この干渉縞の作
用によって被検体表面に干渉縞間隔と同じ間隔を持つ歪
み分布を形成することによって、被検体内部および表面
を伝搬する弾性波の音速と干渉縞の走査速度の比で決ま
る方向に、当該弾性波を放射することを特徴としてい
る。In order to solve this problem, the elastic wave generating method of the present invention is designed such that two coherent energy beams having slightly different frequencies are cross-irradiated on a subject, By generating interference fringes to be scanned and forming a strain distribution having the same spacing as the interference fringe spacing on the surface of the subject by the action of the interference fringes, the sound velocity of the elastic wave propagating inside and on the subject and the interference fringes. The elastic wave is radiated in the direction determined by the ratio of the scanning speeds.
【０００８】[0008]
【作用】周波数のわずかに異なる２本のレーザービーム
を被検体上で交差させて照射して、高速で走査される干
渉縞を生成し、光吸収による熱弾性効果または光の電場
による電歪効果によって被検体上に干渉縞間隔と同じ間
隔の歪み分布を形成する。この歪み分布は、レーザーの
周波数差と同じ周波数で変動するので、この歪み分布か
ら放射される弾性波は、被検体法線から測って、弾性波
の音速と縞の走査速度の比の逆正弦で与えられる角度を
なす方向に強い指向性を持って放射される。[Function] Two laser beams having slightly different frequencies are crossed and irradiated on the subject to generate interference fringes scanned at high speed, and a thermoelastic effect due to light absorption or an electrostriction effect due to an electric field of light is generated. Thus, a strain distribution having the same spacing as the interference fringe spacing is formed on the subject. Since this strain distribution fluctuates at the same frequency as the frequency difference of the laser, the elastic wave radiated from this strain distribution is the inverse sine of the ratio of the acoustic velocity of the elastic wave to the scanning velocity of the stripes, measured from the normal to the subject. Is emitted with a strong directivity in the direction of the angle given by.
【０００９】[0009]
【実施例】以下、この発明の詳細を一実施例を示す図面
について説明する。まず、この発明の方法による弾性波
の発生原理を詳細に説明する。図１に示すように、異な
る角周波数ω1 ，ω2 を持つ２つのエネルギービーム、
例えば２つのレーザービーム１および２を、被検体３の
面に法線と入射角度θをなす方向に入射させる。エネル
ギービームとしてはレーザービームのほか電子線等も使
用することができる。２本のビームは、音響光学素子に
より周波数差を与えられるか、２つの周波数で同時発振
するレーザーの個々のビームとする。この２つレーザー
ビームの干渉により、Ｉ1 をレーザービーム１の振幅、
Ｉ2 をレーザービーム２の振幅として、被検体表面での
光の振幅Ｉと強度Ｉ2 は以下の様になる。 Ｉ＝Ｉ1 expj（ｋ1 ｘ−ω1 ｔ）＋Ｉ2 expj（ｋ2 ｘ−ω2 ｔ） Ｉ2 ＝Ｉ1 2 ＋Ｉ2 2 ＋２Ｉ1 Ｉ2 cos ｛（２Ｋsin θ）ｘ−ωa ｔ｝ （１） ここで、ｋ1 、ｋ2 はレーザービームの波数ベクトル
で、 Ｋ＝｜ｋ1 ｜＝｜ｋ2 ｜＝２π／λ （２） はレーザーの波数の大きさ、λはレーザーの波長、 ωa ＝ω2 −ω1 （３） は２つのレーザービームの角周波数差である。式（１）
の第３項は図１において黒□で示したような干渉縞を表
し、その間隔は Λ＝λ／２sin θ （４） で与えられ、その走査速度は、 Ｖ＝ωa ／２Ｋsin θ （５） となることが導かれる。この干渉縞のもたらす光吸収や
光の電場により干渉縞の強度分布と同じ周期を持つ歪み
が被検体表面に形成され、この歪みは弾性波として物体
表面沿いおよび内部に向けて放射される。この際、内部
に放射される弾性波の波面と被検体表面の交点が、干渉
縞の間隔と等しい間隔を持ち、干渉縞の走査速度Ｖと等
しい速度を持つ場合には、レーザーが発光し干渉縞が存
在する間、弾性波は増幅されるので、特に強い弾性波が
発生される。この条件を満たすのは、次式によって与え
られる方向に放射される弾性波である。 φ＝sin -1（ｖ／Ｖ） （６） ここで、φは物体表面の法線方向と弾性波の伝搬方向の
なす角度、ｖは弾性波の音速である。以上が効果的にバ
ルク弾性波を発生する場合の原理である。次に、特に走
査速度Ｖが弾性表面の音速ｖR に等しい場合、（６）式
の音速ｖとしてｖR を取るとφ＝９０度となり、表面に
沿って弾性表面波が発生する。これが弾性表面波を発生
する方法の原理である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings showing an embodiment. First, the principle of generation of elastic waves by the method of the present invention will be described in detail. As shown in FIG. 1, two energy beams with different angular frequencies ω 1 and ω 2 ,
For example, the two laser beams 1 and 2 are made incident on the surface of the subject 3 in a direction forming an incident angle θ with the normal. As the energy beam, an electron beam or the like can be used in addition to the laser beam. The two beams are individual beams of a laser that are given a frequency difference by an acousto-optic device or that oscillate simultaneously at two frequencies. Due to the interference of these two laser beams, I 1 is the amplitude of the laser beam 1,
With I 2 as the amplitude of the laser beam 2, the amplitude I and the intensity I 2 of the light on the surface of the subject are as follows. I = I 1 expj (k 1 x−ω 1 t) + I 2 expj (k 2 x−ω 2 t) I 2 = I 1 2 + I 2 2 + 2I 1 I 2 cos {(2Ksin θ) x−ω a t } (1) Here, k 1 and k 2 are wave number vectors of the laser beam, and K = | k 1 | = | k 2 | = 2π / λ (2) is the wave number of the laser, and λ is the wave number of the laser. The wavelength, ω a = ω 2 −ω 1 (3) is the angular frequency difference between the two laser beams. Formula (1)
The third term of is the interference fringe as shown by the black square in FIG. 1, the interval is given by Λ = λ / 2sin θ (4), and the scanning speed is V = ω a / 2Ksin θ (5 ) Is introduced. Due to the light absorption and the electric field of the light produced by the interference fringes, a strain having the same period as the intensity distribution of the interference fringes is formed on the surface of the subject, and the strain is radiated as an elastic wave toward and along the surface of the object. At this time, if the intersection of the wavefront of the elastic wave radiated inside and the surface of the subject has an interval equal to the interval of the interference fringes and a speed equal to the scanning speed V of the interference fringes, the laser emits light and interferes. Since the elastic wave is amplified while the stripes are present, a particularly strong elastic wave is generated. This condition is satisfied by the elastic wave radiated in the direction given by the following equation. φ = sin −1 (v / V) (6) Here, φ is the angle formed by the normal direction of the object surface and the propagation direction of the elastic wave, and v is the acoustic velocity of the elastic wave. The above is the principle for effectively generating bulk acoustic waves. Next, particularly when the scanning velocity V is equal to the sound velocity v R of the elastic surface, when v R is taken as the sound velocity v of the equation (6), φ = 90 degrees, and a surface acoustic wave is generated along the surface. This is the principle of the method of generating surface acoustic waves.
【００１０】（実験例）この発明を実施するには、目的
とする周波数帯の弾性波の周期（１〜１０ｎｓ程度）よ
り十分長いパルス幅を持ち、干渉性がよいパルスレーザ
ーの使用が望ましい。実験装置の概略を図２に示す。レ
ーザーとして、波長５３２nm、パルス幅２００ns、エネ
ルギー５mJ、ビーム径５mm（被検体面上）のレーザー発
生装置３から発生したNd：YAG Ｑスイッチパルスレーザ
ーの第二高調波を使用した。このレーザービームをビー
ムスプリッタで分割した後、一方のビーム１を周波数を
変移させるためＴｅＯ2 製音響光学（Acousttooptic;A
O) 素子５（周波数ωは１１０ＭＨｚ）を用いた。周波
数変移レーザビーム２および未変移レーザービーム１は
それぞれ厚さ１．５ｍｍのアルミニウム板６へ入射角θ
（図１）＝０．３度で照射した。これによって間隔５
０．８μｍの干渉縞が速度５５８８ｍ／ｓで走査され
る。この結果、発生した横波弾性波はアルミニウム板６
を透過してレーザー干渉縞照射面と反対側の水滴７中に
放射される。そこで、この水滴を弾性波伝搬媒体として
設置した超音波センサによって検出した。符号１２はオ
シロスコープである。(Experimental Example) In order to carry out the present invention, it is desirable to use a pulse laser having a pulse width sufficiently longer than the period (about 1 to 10 ns) of an elastic wave in a target frequency band and having good coherence. The outline of the experimental apparatus is shown in FIG. As the laser, the second harmonic of the Nd: YAG Q switch pulse laser generated from the laser generator 3 having a wavelength of 532 nm, a pulse width of 200 ns, an energy of 5 mJ, and a beam diameter of 5 mm (on the surface of the subject) was used. After splitting this laser beam with a beam splitter, one of the beams 1 is made of TeO 2 for changing the frequency.
O) Element 5 (frequency ω is 110 MHz) was used. The frequency-shifted laser beam 2 and the unshifted laser beam 1 are incident on the aluminum plate 6 having a thickness of 1.5 mm by an incident angle θ.
(Fig. 1) = 0.3 degree irradiation. This gives an interval of 5
Interference fringes of 0.8 μm are scanned at a speed of 5588 m / s. As a result, the transverse elastic wave generated is generated by the aluminum plate 6.
And is emitted into the water droplet 7 on the side opposite to the laser interference fringe irradiation surface. Therefore, this water drop was detected by an ultrasonic sensor installed as an elastic wave propagation medium. Reference numeral 12 is an oscilloscope.
【００１１】図３の上段の波形はレーザー光を検出する
フォトダイオード１１の出力で、レーザーパルスの時間
変化を示す。下段の信号は超音波センサからの出力波形
を示す。測定時間範囲は１０マイクロ秒である。図４は
超音波センサの波形を明瞭に観測するため、時間軸を拡
大したもので、測定時間範囲は０．２マイクロ秒であ
る。この場合、明瞭な周期的信号が観測され、時間変化
の周期から、周波数１１０ＭＨｚを持つことが解った。The waveform at the top of FIG. 3 is the output of the photodiode 11 which detects the laser light, and shows the change over time of the laser pulse. The lower signal shows the output waveform from the ultrasonic sensor. The measurement time range is 10 microseconds. In FIG. 4, the time axis is enlarged to clearly observe the waveform of the ultrasonic sensor, and the measurement time range is 0.2 microseconds. In this case, a clear periodic signal was observed, and it was found that the frequency was 110 MHz from the period of time change.
【００１２】以上の結果より本発明の方法で周波数１１
０ＭＨｚの横波が励起されていることが確認された。ま
た、実験では２つのレーザービームのうち任意の１つを
さえぎると波形が消失することを確認した。また、図
３，図４ともにアベレージングはおこなわずに得られた
結果であるにもかかわらず、信号対雑音（Ｓ／Ｎ）比は
３０db以上あった。さらにこの実験では被検体表面にレ
ーザー照射による熱損傷発生しなかった。これは照射面
におけるパワー密度が０．１３ＭＷ／ｃｍ2 と低いため
で、この発明による弾性波の発生方法の低損傷性を実証
するものである。From the above results, the frequency of 11
It was confirmed that the 0 MHz transverse wave was excited. In addition, in the experiment, it was confirmed that the waveform disappeared when any one of the two laser beams was blocked. In addition, the signal-to-noise (S / N) ratio was 30 db or more, although the results were obtained without averaging in both FIGS. Furthermore, in this experiment, no thermal damage was caused on the surface of the subject by laser irradiation. This is because the power density on the irradiated surface is as low as 0.13 MW / cm 2 , which demonstrates the low damage of the elastic wave generation method according to the present invention.
【００１３】[0013]
【発明の効果】この発明の弾性波の発生方法では、レー
ザーのパルス幅が弾性波の周期より十分大きい場合、歪
みの積算効果によって大振幅が実現できる。これは従来
の「レーザー超音波法」に比べて、検査と計測の大幅な
感度能向上をもたらすことができる。また、この発明の
弾性波の発生方法では、発生する弾性波は（６）式で与
えられる方向へ伝搬するので、干渉縞の走査速度を制御
することによって弾性波の放射方向の制御が可能であ
る。また、この発明の弾性波の発生方法では、ビームの
エネルギーはビーム径の大きさに分散するので、物体表
面でのエネルギー密度を低くでき、物体の損傷がおきに
くい。また、従来の「単一ビーム走査法」では、高周波
化が困難だが、本発明の方法では、ビームの交差角度と
周波数差を大きくすれば、任意の周波数の弾性波が発生
できる。さらに、従来の「光ファイバーフェーズドアレ
イ法」ではできなかった、周波数と指向性の独立制御が
可能である。According to the elastic wave generating method of the present invention, when the pulse width of the laser is sufficiently larger than the period of the elastic wave, a large amplitude can be realized by the effect of integrating the distortion. This can bring about a significant improvement in the sensitivity of inspection and measurement as compared with the conventional “laser ultrasonic method”. Further, in the elastic wave generating method of the present invention, since the generated elastic wave propagates in the direction given by the equation (6), the emission direction of the elastic wave can be controlled by controlling the scanning speed of the interference fringes. is there. Further, in the elastic wave generating method of the present invention, the energy of the beam is dispersed in the size of the beam diameter, so that the energy density on the surface of the object can be lowered and the object is less likely to be damaged. Further, it is difficult to increase the frequency by the conventional “single beam scanning method”, but in the method of the present invention, an elastic wave of an arbitrary frequency can be generated by increasing the beam crossing angle and the frequency difference. Furthermore, independent control of frequency and directivity is possible, which was not possible with the conventional “optical fiber phased array method”.
【図１】この発明の原理を示す構成説明図。FIG. 1 is a structural explanatory view showing the principle of the present invention.
【図２】この発明の実験例を与える実験装置の構成説明
図。FIG. 2 is an explanatory diagram of a configuration of an experimental device that gives an experimental example of the present invention.
【図３】図２の実験装置で測定された、レーザーのパル
ス波形（上段）および厚さ１．５ｍｍのアルミニウム板
に発生させた周波数１１０ＭＨｚの横波弾性波の検出信
号波形（下段）を示すグラフ。FIG. 3 is a graph showing a laser pulse waveform (upper stage) and a detection signal waveform of a transverse elastic wave with a frequency of 110 MHz generated in an aluminum plate having a thickness of 1.5 mm (lower stage) measured by the experimental apparatus of FIG. .
【図４】図３の横波弾性波の波形の拡大図で、周波数が
１１０ＭＨｚであることを確認できる波形を示すグラ
フ。FIG. 4 is an enlarged view of the waveform of the transverse elastic wave in FIG. 3, which is a graph showing the waveform with which the frequency can be confirmed to be 110 MHz.
１ レーザービーム ２ レーザービーム ３ レーザー発生装置 ４ ビームスプリッタ ５ ＴｅＯ2 製音響光学素子 ６ アルミニウム板 ７ 水滴 ８ 超音波センサ １１ フォトダイオード １２ オシロスコープ1 Laser Beam 2 Laser Beam 3 Laser Generator 4 Beam Splitter 5 TeO 2 Acousto-Optic Element 6 Aluminum Plate 7 Water Droplet 8 Ultrasonic Sensor 11 Photodiode 12 Oscilloscope
───────────────────────────────────────────────────── フロントページの続き (72)発明者 西野 秀郎 東京都台東区台東一丁目５番１号 凸版印 刷株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Nishino 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.
Claims (4)
ネルギービームを被検体上で交差させて照射して、走査
される干渉縞を生成し、この干渉縞の作用によって被検
体表面に干渉縞間隔と同じ間隔を持つ歪み分布を形成す
ることによって、前記被検体内部または表面を伝搬する
弾性波の音速と干渉縞の走査速度の比で決まる方向に、
前記弾性波を放射することを特徴とする弾性波の発生方
法。1. A coherent energy beam having two slightly different frequencies is cross-irradiated on a subject to generate interference fringes to be scanned, and the interference fringes are formed on the surface of the subject by the action of the interference fringes. By forming a strain distribution having the same spacing as the spacing, in the direction determined by the ratio of the acoustic velocity of the elastic wave propagating inside the subject or the surface and the scanning velocity of the interference fringes,
A method of generating elastic waves, characterized in that the elastic waves are radiated.
面波の音速に等しい速度で干渉縞を走査することによっ
て、弾性表面波を発生させることを特徴とする請求項１
記載の弾性波の発生方法。2. The surface acoustic wave is generated by scanning the interference fringes at a velocity equal to the speed of sound of the surface acoustic wave propagating along the surface of the subject.
A method for generating an elastic wave as described.
ことを特徴とする請求項１記載の弾性波の発生方法。3. The method for generating elastic waves according to claim 1, wherein the object is a solid, a liquid, a gel, or the like.
ー、電子線などであることを特徴とする請求項１記載の
弾性波の発生方法。4. The method for generating an elastic wave according to claim 1, wherein the coherent energy beam is a laser, an electron beam, or the like.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4355522A JPH0774795B2 (en) | 1992-12-18 | 1992-12-18 | Bulk elastic wave generation method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4355522A JPH0774795B2 (en) | 1992-12-18 | 1992-12-18 | Bulk elastic wave generation method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06186208A true JPH06186208A (en) | 1994-07-08 |
| JPH0774795B2 JPH0774795B2 (en) | 1995-08-09 |
Family
ID=18444428
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4355522A Expired - Lifetime JPH0774795B2 (en) | 1992-12-18 | 1992-12-18 | Bulk elastic wave generation method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0774795B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5796004A (en) * | 1995-10-24 | 1998-08-18 | Toppan Printing Co., Ltd. | Method and apparatus for exciting bulk acoustic wave |
| KR101008172B1 (en) * | 2008-09-23 | 2011-01-13 | 주식회사 포스코 | Laser Ultrasonic Testing Using Thermoelastic Effects of Laser Pulsed Beams |
| JP2011107119A (en) * | 2009-11-16 | 2011-06-02 | Samsung Electro-Mechanics Co Ltd | Circuit pattern defect inspection method of substrate |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4541280A (en) * | 1982-12-28 | 1985-09-17 | Canadian Patents & Development Ltd. | Efficient laser generation of surface acoustic waves |
-
1992
- 1992-12-18 JP JP4355522A patent/JPH0774795B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4541280A (en) * | 1982-12-28 | 1985-09-17 | Canadian Patents & Development Ltd. | Efficient laser generation of surface acoustic waves |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5796004A (en) * | 1995-10-24 | 1998-08-18 | Toppan Printing Co., Ltd. | Method and apparatus for exciting bulk acoustic wave |
| KR101008172B1 (en) * | 2008-09-23 | 2011-01-13 | 주식회사 포스코 | Laser Ultrasonic Testing Using Thermoelastic Effects of Laser Pulsed Beams |
| JP2011107119A (en) * | 2009-11-16 | 2011-06-02 | Samsung Electro-Mechanics Co Ltd | Circuit pattern defect inspection method of substrate |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0774795B2 (en) | 1995-08-09 |
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