JPS6330758A - Detection of surface flaw - Google Patents
Detection of surface flawInfo
- Publication number
- JPS6330758A JPS6330758A JP61173575A JP17357586A JPS6330758A JP S6330758 A JPS6330758 A JP S6330758A JP 61173575 A JP61173575 A JP 61173575A JP 17357586 A JP17357586 A JP 17357586A JP S6330758 A JPS6330758 A JP S6330758A
- Authority
- JP
- Japan
- Prior art keywords
- light beam
- sample
- photoacoustic signal
- flaw
- sample surface
- 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
- 238000001514 detection method Methods 0.000 title claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 20
- 230000007547 defect Effects 0.000 claims description 57
- 239000000919 ceramic Substances 0.000 description 8
- 230000008859 change Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000010355 oscillation Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009412 basement excavation Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000005236 sound signal Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Landscapes
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
Description
【発明の詳細な説明】
〔発明の技術分野］
本発明は、構造用セラミックス等の試料の欠陥検出に適
用して有用な光音響法による表面欠陥検出方法に係わり
、特に湾曲した試料の欠陥検出に好適する表面欠陥検出
方法に関する。[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a surface defect detection method using a photoacoustic method that is useful for detecting defects in samples such as structural ceramics, and in particular, the present invention relates to a surface defect detection method using a photoacoustic method that is useful for detecting defects in samples such as structural ceramics. The present invention relates to a surface defect detection method suitable for.
〔発明の技術的背景とその問題点）
高温高強度材料として注目されている構造用セラミック
スは、脆性材料であるために微小な欠陥、特に表面近傍
の欠陥の存在が著しい強度低下をもたらす。この強度低
下の原因で必る微小欠陥を非破壊的に検出する方法とし
て、従来より、超音波探傷法やＸｔｇＡ深傷法深厚法い
られていた。[Technical background of the invention and its problems] Structural ceramics, which are attracting attention as high-temperature, high-strength materials, are brittle materials, and the presence of minute defects, especially defects near the surface, causes a significant decrease in strength. Ultrasonic flaw detection and XtgA deep flaw detection have conventionally been used as methods for non-destructively detecting the minute defects that are the cause of this strength reduction.
しかしこれらの従来の方法は、元来金属等の延性材料を
対象とするものであり、その検出限界は数１００［μｍ
］以上である場合が多い。このため、数１０「μｒｎＪ
の欠陥が破壊の原因となる構造用セラミックスにはその
まま適用づることか難しい。取分け、著しい強度低下を
もたらす表面直下の欠陥の検出は、上記した従来法では
原理的に困難である。However, these conventional methods originally target ductile materials such as metals, and their detection limit is several hundred μm.
] or more in many cases. For this reason, the number 10 “μrnJ
It is difficult to directly apply this method to structural ceramics, where defects can cause failure. In particular, it is difficult in principle to detect defects just below the surface that cause a significant decrease in strength using the conventional methods described above.
一方、物質の表面状態を非破壊点に評価する方法として
、光音響法が顕微鏡等に適用されている。On the other hand, the photoacoustic method is applied to microscopes and the like as a method for non-destructively evaluating the surface state of substances.
この方法は、強度変調された光ビーム、例えばチョッパ
により断続された光ビームを試料表面に照射した時に、
試料が断続的な熱吸収により発生する音波をマイクロフ
ォンで検出するものである。In this method, when the sample surface is irradiated with an intensity-modulated light beam, for example, a light beam interrupted by a chopper,
This method uses a microphone to detect the sound waves generated by the intermittent heat absorption of the sample.
このマイクロフォンにより検出された信号を光音響信号
と言い、欠陥のない正常な試料ではその試料に固有の一
定の応答レベルを示す。試料の表面ビームの試料上での
スポット径で決まり、微小な欠陥を検出するためには、
その欠陥の大きさ程度まで光ビームを絞り込む必要があ
る。例えば、数１０［μｍ］の欠陥に対して１［履］程
度の光ビームスポットを照射しても、欠陥による異常応
答をＳ／Ｎ良く検出することができないからである。The signal detected by this microphone is called a photoacoustic signal, and a normal sample with no defects exhibits a certain response level unique to that sample. It is determined by the spot diameter of the sample surface beam on the sample, and in order to detect minute defects,
It is necessary to narrow down the light beam to the size of the defect. This is because, for example, even if a light beam spot of about 1 [μm] is irradiated onto a defect of several tens [μm], an abnormal response due to the defect cannot be detected with a good S/N ratio.
そこで例えば、ＡｒレーザやＨｅ−Ｎｅレーザ等から得
られる光ビームを集光レンズによって微小スポットとし
て試料表面に集光することになる。Therefore, for example, a light beam obtained from an Ar laser, a He-Ne laser, or the like is focused on the sample surface as a minute spot using a condensing lens.
光音響法による表面欠陥検出法を平面状のセラミックス
に適応する場合、絶えず光ビームを絞り込んだ状態で使
用できると言う利点がある。これに対し、湾曲したセラ
ミックスの場合には光ビームを走査すると、試料の高さ
変動により試料表面に当たるビーム径が可変する。この
ため、試料表面でのご一ム径が一定値以上になり、必ず
しも同−精、度で欠陥検出ができないと言う欠点がある
。When applying the surface defect detection method using the photoacoustic method to planar ceramics, there is an advantage that the light beam can be used in a constantly focused state. On the other hand, when scanning a curved ceramic with a light beam, the diameter of the beam hitting the sample surface changes due to changes in the height of the sample. For this reason, the diameter of the grain on the sample surface exceeds a certain value, and there is a drawback that defects cannot necessarily be detected with the same precision and accuracy.
なお、単一ビームから得られる光音響信号が最大になる
よう、試料表面からの絞り込み用レンズ位置を変化させ
るには多くの時間を要し、実用的で−）Ｆい・
電
１、〔発明の目的］
］１ 本発明は上記事情を考慮してなされたもので・そ
の目的とするところは、光音響法を利用して、湾曲した
試料表面及び表面直下の微小欠陥を精度良く検出するこ
とができるようにした表面欠陥検出方法を提供すること
にある。It should be noted that it takes a lot of time to change the position of the focusing lens from the sample surface so that the photoacoustic signal obtained from a single beam is maximized. [Purpose of the invention]] 1. The present invention was made in consideration of the above-mentioned circumstances.The purpose of the present invention is to use photoacoustic method to accurately detect minute defects on a curved sample surface and directly below the surface. An object of the present invention is to provide a method for detecting surface defects that enables the detection of surface defects.
本発明の骨子は、２本の光ビームを用い、第１の光ビー
ムの照射により試料表面に照射される光ビームが常に微
小スポットとなるよう集光度合いを制御し、第２の光ビ
ームの照射により試料表面の欠陥を検出することにある
。The gist of the present invention is to use two light beams, control the degree of condensation so that the light beam irradiated onto the sample surface by the irradiation of the first light beam always forms a minute spot, and The purpose is to detect defects on the surface of a sample by irradiation.
即ち本発明は、強度変調された光ビームにより試料表面
を走査し、試料から得られる光音響信号を検出して試料
の表面若しくはその直下の欠陥を検出する表面欠陥検出
方法において、異なる周波数で変調された２本の光ビー
ムを試料表面の近接した異なる２点に集光し、第１の光
ビームの照射による光音響信号に基づいて試料表面の高
さ変動量を検出し、該高さ変動量に応じて第２の光ビー
ムが試料表面に微小スポットとして集光するよう調節し
、この状態で第２の光ビームの照射による光音響信号に
基づいて前記欠陥検出を行うようにした方法である。That is, the present invention provides a surface defect detection method in which a sample surface is scanned with an intensity-modulated light beam and a photoacoustic signal obtained from the sample is detected to detect a defect on the sample surface or directly below. The two light beams thus generated are focused on two different points close to each other on the sample surface, and the amount of height variation on the sample surface is detected based on the photoacoustic signal generated by the irradiation with the first light beam. In this method, the second light beam is adjusted so as to be focused on the sample surface as a minute spot according to the amount of light, and in this state, the defect detection is performed based on a photoacoustic signal generated by irradiation with the second light beam. be.
なお、２本の光ビームを試料表面に同時に照射しても、
各ビームの周波数が異なることから、同期検波等の手法
によりそれぞれのビーム照射に対応する光音響信号を独
立に取出すことができる。Note that even if two light beams are irradiated onto the sample surface at the same time,
Since each beam has a different frequency, it is possible to independently extract photoacoustic signals corresponding to each beam irradiation using a technique such as synchronous detection.
また、第１の光ビームの照射位置に基づいて第２の光ビ
ームの焦点合わせを行っていることから、第１及び第２
の光ビームの照射位置は近い方が望ましい。但し、第１
及び第２の光ビームの照射位置が同じであると、第１の
光ビームの照射による吸収熱等の影響で第２の光ビーム
の照射による光音響信号にノイズ等が生じる虞れがある
ので、第１及び第２のビーム光ビームの照射位置は、そ
れぞれの照射位置が重ならない程度離した方が望ましい
。In addition, since the second light beam is focused based on the irradiation position of the first light beam, the first and second light beams are
It is desirable that the irradiation position of the light beam be closer. However, the first
If the irradiation positions of the first light beam and the second light beam are the same, there is a risk that noise etc. will occur in the photoacoustic signal caused by the irradiation of the second light beam due to the effects of heat absorbed by the irradiation of the first light beam. It is preferable that the irradiation positions of the first and second light beams are separated to an extent that the respective irradiation positions do not overlap.
（発明の効果〕
本発明によれば、焦点合わせ用及び欠陥検出用の２本の
光ビームを用いているので、それぞれのビームに基づい
て焦点合わせ及び欠陥検出を高精度に行うことができる
。即ち、欠陥検出を行うには、光ビームの径は小さく周
波数は高い方が望ましい。一方、欠陥検出に適した光ビ
ームを用いて焦点合わせを行うと、欠陥の有無により光
音響信号が変化するので、高精度の焦点合わせを行うこ
とは困難である。つまり、焦点合わせを行うには、光ビ
ームの径は大きく周波数は低い方が望ましい。(Effects of the Invention) According to the present invention, since two light beams are used, one for focusing and one for defect detection, focusing and defect detection can be performed with high precision based on the respective beams. In other words, for defect detection, it is desirable that the diameter of the light beam be small and the frequency be high.On the other hand, when focusing is performed using a light beam suitable for defect detection, the photoacoustic signal changes depending on the presence or absence of defects. Therefore, it is difficult to perform highly accurate focusing.In other words, in order to perform focusing, it is desirable that the diameter of the light beam be large and the frequency be low.
従って、本発明のように２本の光ビームを用い、それぞ
れの光ビームを焦点合わせ用及び欠陥検出用に最適な周
波数及びビーム径とすることにより、せることができ、
この状態で第２の光ビームの照射による光音響信号に基
づいて欠陥検出を行うことができる。このため、湾曲し
た試Ｉｔであっても、その表面及び表面直下の微小欠陥
を高精度に検出することができ−る。Therefore, by using two light beams as in the present invention and setting each light beam to the optimal frequency and beam diameter for focusing and defect detection, it is possible to
In this state, defects can be detected based on a photoacoustic signal generated by irradiation with the second light beam. Therefore, even if the sample is curved, minute defects on the surface and just below the surface can be detected with high precision.
以下、本発明の詳細を図示の実施例によって説明する。 Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.
第１図は本発明の一実施例方法に使用した表面欠陥検出
装置を示ｖＩＲ１８構成図である。図中１１は第１のレ
ーザ管、２１は第２のレーザ管であり、これらのレーザ
管１１．２１はＨｅ−ＮｅレーザやＡｒレーザ等からな
るものである。レーザ管１１．２１から放射された光ビ
ームは、第１及び第２のメカニカルチョッパ１２．２２
によりそれぞれ断続光ビームに変調される。メカニカル
チョッパ１２．２２は、第１及び第２の発振器１３゜２
３の発振周波数ｆｌ、ｆ２に同期してレーザ光ビームを
それぞれ断続するものである。メカニカルチョッパ１２
．２２により変調された第１及び試料３０は、タービン
ブレード等の湾曲した形状の構造用セラミックスであり
、セル３１内に配置されている。セル３１の上端開口に
は、石英ガラスからなる光透過窓３２が設けられており
、前記光ビーム１４．２４はこの窓３２を透過して試料
表面に照射される。また、セル３１の下部にはマイクロ
フォン３３が埋設されており、上記光ビーム１４．２４
の照射による試料３０からの光音５信号が噴出されるも
のとなっている。なお、図には示さないが試料表面での
光ビームの照射位置を変えるために、セル３１には移動
機構が設けられており、この移ａ ｍ ＋ｉによりセル
３１は紙面左右方向及び表裏方向に移動されるものとな
っている。また、セル３１を移動する代りに、光ビーム
１４．２４を試料表面上で走査するようにしてもよい。FIG. 1 is a block diagram of vIR18, showing a surface defect detection device used in a method according to an embodiment of the present invention. In the figure, 11 is a first laser tube, and 21 is a second laser tube, and these laser tubes 11 and 21 are made of a He-Ne laser, an Ar laser, or the like. The light beam emitted from the laser tube 11.21 is transmitted to the first and second mechanical choppers 12.22.
are respectively modulated into intermittent light beams. The mechanical chopper 12.22 has first and second oscillators 13°2
The laser beams are intermittent in synchronization with the oscillation frequencies fl and f2 of No. 3, respectively. mechanical chopper 12
．． The first sample 30 modulated by 22 is a structural ceramic with a curved shape, such as a turbine blade, and is placed in a cell 31 . A light transmission window 32 made of quartz glass is provided at the upper end opening of the cell 31, and the light beam 14.24 passes through this window 32 and is irradiated onto the sample surface. Further, a microphone 33 is buried in the lower part of the cell 31, and the light beam 14.24 is
Five optical sound signals are emitted from the sample 30 by the irradiation. Although not shown in the figure, the cell 31 is provided with a moving mechanism in order to change the irradiation position of the light beam on the sample surface, and this movement a It is expected to be moved. Furthermore, instead of moving the cell 31, the light beam 14.24 may be scanned over the sample surface.
マイクロフォン３３で検出された光音響信号は、第１及
び第２のロックインアンプ１７．２７にそれぞれ供給さ
れる。第１のロックインアンプ１７では、上記入力した
信号を前記第１の発ｆｉ！器１３の発振周波数ｆ１を参
照信号として第１の光ビーム１４の照射による光音響信
号のみが検出される。The photoacoustic signals detected by the microphone 33 are supplied to the first and second lock-in amplifiers 17.27, respectively. The first lock-in amplifier 17 converts the input signal into the first output fi! Only the photoacoustic signal caused by the irradiation of the first light beam 14 is detected using the oscillation frequency f1 of the device 13 as a reference signal.
ロックインアンプ１７の出力信号は集光レンズ制御回路
１８に供給される。この制御回路１８は、第１及び第２
の集光レンズ位置調整機構１９゜２９を制御するもので
あり、光音Ｂ信号が所定レベル以下となるとき、上記調
整機構１９．２９による集光レンズ１６．２６の位置を
調整する。これにより、第１及び第２の光ビーム１４．
２４は試料３０の湾曲に拘らず、常に試料表面に集光す
るものとなっている。The output signal of the lock-in amplifier 17 is supplied to a condensing lens control circuit 18. This control circuit 18 includes first and second
When the optical sound B signal becomes below a predetermined level, the position of the focusing lens 16.26 is adjusted by the adjusting mechanism 19.29. This causes the first and second light beams 14.
24 always focuses light on the surface of the sample regardless of the curvature of the sample 30.
ここで、試料３０が湾曲していると、光ビーム照射位置
により試料３Ｑの高さ位置が変動し、試料３０から集光
レンズ１６までの距離が変化する。Here, if the sample 30 is curved, the height position of the sample 3Q changes depending on the light beam irradiation position, and the distance from the sample 30 to the condenser lens 16 changes.
この距離の変化により、光音響信号は第２図に示す如く
変化する。つまり、焦点がずれた場合に光音響信号のレ
ベルが著しく低下する。そこで、集光レンズ制御回路１
８では、光音響信号のレベルが一定値以下となるとき、
集光レンズ位置調整機構１９に制御信号を送り、集光レ
ンズ１６の位置を調整し、試料３０から集光レンズ１６
までの距離がＡの範囲となるように制御している。さら
に、集光レンズ１６の位置調整に同期して集光レンズ２
６の位置を調整し、試料３０の表面から集光レンズ２６
までの距離が予め定められた距離範囲内となるように制
御している。Due to this distance change, the photoacoustic signal changes as shown in FIG. That is, when the focus shifts, the level of the photoacoustic signal drops significantly. Therefore, the condenser lens control circuit 1
8, when the level of the photoacoustic signal is below a certain value,
A control signal is sent to the focusing lens position adjustment mechanism 19 to adjust the position of the focusing lens 16, and the focusing lens 16 is moved from the sample 30 to the focusing lens 16.
The distance is controlled so that it falls within the range A. Furthermore, in synchronization with the position adjustment of the condenser lens 16, the condenser lens 2
Adjust the position of the condenser lens 26 from the surface of the sample 30.
The distance to the vehicle is controlled so that it is within a predetermined distance range.
また、第２のロックインアンプ２７では、上記入力した
信号を前記第２の発撮器２３の発掘周波数ｆ２を参照信
号として＠２の光ビーム２４の照射による光音響信号の
みが検出される。そして、このロックインアンプ２７の
出力信号がレコーダ２８に供給され、このレコーダ２８
により試料３０の表面欠陥の有無に対応した光音響信号
が記録されるものとなっている。Further, in the second lock-in amplifier 27, only the photoacoustic signal caused by the irradiation of the light beam 24 of @2 is detected using the input signal as a reference signal and the excavation frequency f2 of the second oscillator 23. Then, the output signal of this lock-in amplifier 27 is supplied to the recorder 28, and this recorder 28
Accordingly, a photoacoustic signal corresponding to the presence or absence of a surface defect on the sample 30 is recorded.
次に、上記装置を用いた表面欠陥検出方法について説明
する。Next, a method for detecting surface defects using the above device will be explained.
まず、第１の光ビーム１４の周波数ｆ１を５０［Ｈｚ］
、試料表面上での設定ビーム径Ｄ１を２００［μｍ］、
第２の光ビーム２４の周波数を１ ［ＫＨｚ］、試料表
面上での設定ビーム径Ｄ２を１０［μ７７１］とした。First, the frequency f1 of the first light beam 14 is set to 50 [Hz].
, the set beam diameter D1 on the sample surface is 200 [μm],
The frequency of the second light beam 24 was 1 [KHz], and the set beam diameter D2 on the sample surface was 10 [μ771].
また、第１及び第２の光ビーム１４．２４の試料表面で
の照射位置は数１００［μ７７１］程度離した。Furthermore, the irradiation positions of the first and second light beams 14.24 on the sample surface were separated by about several hundred [μ771].
上記の条件で、欠陥のない湾曲した試料３０としてター
ビンブレードを用い、その欠陥検出操作を行ったところ
、レコーダ２８に記録された光音響信号は略一定であっ
た。つまり、第１の光ビーム１４の照射による光音響信
号に基づいて集光レンズ１６．２６の位置を調整するこ
とにより、第２の光ビーム２４を常に試料表面に微小ス
ポット光として集光させることができ、試料表面の高さ
変動による影響をなくすことができた。When a defect detection operation was performed under the above conditions using a turbine blade as a defect-free curved sample 30, the photoacoustic signal recorded on the recorder 28 was approximately constant. That is, by adjusting the position of the condenser lens 16.26 based on the photoacoustic signal generated by the irradiation of the first light beam 14, the second light beam 24 can be constantly focused on the sample surface as a minute spot light. This made it possible to eliminate the effects of height fluctuations on the sample surface.
次いで、上記試料３０にビッカース圧子で人工゛゛１
″埒陥を作り、同様の欠陥検出操作を行ったところ、レ
コーダ２８に記録された光音響信号は第３図ｊＪｆ’（
ｉ ａ ） １．：イー、、、４ヶ、え。９．。、え、
。ヶい４分では試料３０の湾曲に関係なく一定であり、
欠陥の存在する部分で光音マ信号が急激に増大している
ことが判った。また、第１の光ビーム１４の照射及び集
光レンズ２６の調整を行わない従来方法と同様にして検
査を行ったところ、レコーダ２８に記録された光音響信
号は第３図（ｂ）に示ず如くなった。つまり、欠陥の存
在しない部分でも光音ｒ４１信号が変化しており、この
ため欠陥検出が非常に困難であった。Next, an artificial defect of ゛゛1'' was made on the sample 30 using a Vickers indenter, and the same defect detection operation was performed, and the photoacoustic signal recorded on the recorder 28 was as shown in Fig.
ia) 1. :Eee...,, 4 months, eh. 9. . ,picture,
. At 4 minutes, it is constant regardless of the curvature of sample 30,
It was found that the photoacoustic signal increased rapidly in the area where the defect existed. In addition, when an inspection was conducted in the same manner as the conventional method without irradiating the first light beam 14 and adjusting the condensing lens 26, the photoacoustic signal recorded on the recorder 28 was as shown in FIG. 3(b). It became like that. In other words, the photoacoustic r41 signal changes even in areas where no defects exist, making it extremely difficult to detect defects.
このように本実施例方法によれば、欠陥検出のための第
２の光ビーム２４とは周波数の異なる第１の光ビーム１
４を試料表面に照射し、この！Ｔ１の光ビーム１４の照
射による光音響信号に基づいて集光レンズ２６の位置を
調整することにより、第２の光ビーム２４を常に試料表
面に微小スポット光として集光させることができる。こ
のため、試料３０が湾曲したものであっても、その湾曲
により光音響信号が変化することはなく、欠陥の検出を
高精度に行うことができる。また、試料３０の高さ変動
検出と欠陥検出のための２本の光ビーーーム径を十分小
さくすることができ、これにより微小欠陥の検出により
有効となる。さらに、試料の高さ変動検出のための第１
の光ビーム１４の周波数ｆ１を十分低くし、試料表面で
のビーム径を′十分大きくすることにより、欠陥の有無
に拘りなく高さ変動を高精度に検出することができる。In this way, according to the method of this embodiment, the first light beam 1 has a different frequency from the second light beam 24 for defect detection.
4 onto the sample surface, this! By adjusting the position of the condenser lens 26 based on the photoacoustic signal generated by the irradiation of the T1 light beam 14, the second light beam 24 can be constantly focused on the sample surface as a minute spot light. Therefore, even if the sample 30 is curved, the photoacoustic signal does not change due to the curve, and defects can be detected with high precision. Furthermore, the diameters of the two light beams for detecting height fluctuations and defects in the sample 30 can be made sufficiently small, which makes the detection of minute defects more effective. Furthermore, the first
By making the frequency f1 of the light beam 14 sufficiently low and making the beam diameter at the sample surface sufficiently large, height fluctuations can be detected with high precision regardless of the presence or absence of defects.
なお、本発明は上述した実施例方法に限定されるもので
はない。例えば、前記第１及び第２の光ビームの周波数
や試料表面でのビーム径等の条件は、検査する試料や必
要とする検出精度等に応じて適宜変更可能である。但し
、欠陥の影響をできるだけ受けないためには、第１の光
ビームの周波数は１００［Ｈｚ］以下、ビーム径は１０
０［μｍ］以上が望ましい。さらに、微小欠陥を検出す
ることから、第２の光ビームの周波数は５００［Ｈｚ］
以上、ビーム径は５０ ［μｍ］以下が望ましい。また
、構造用セラミックスの欠陥検出に限定されるものでは
なく、湾曲した各種試料における微小欠陥の検出に適用
することが可能である。その他、本発明の要旨を逸脱し
ない範囲図はそれぞれ上記装置の作用を説明するための
もので第２図は試料からレンズまでの距離と光音響信号
の強度との関係を示す特性図、第３図は試料位置と光音
響信号の強度との関係を示す特性図である。Note that the present invention is not limited to the method of the embodiment described above. For example, conditions such as the frequency of the first and second light beams and the beam diameter at the sample surface can be changed as appropriate depending on the sample to be inspected, the required detection accuracy, and the like. However, in order to minimize the influence of defects, the frequency of the first light beam should be 100 [Hz] or less, and the beam diameter should be 10
The thickness is preferably 0 [μm] or more. Furthermore, in order to detect minute defects, the frequency of the second light beam is 500 [Hz].
As mentioned above, it is desirable that the beam diameter is 50 [μm] or less. Furthermore, the present invention is not limited to detecting defects in structural ceramics, but can be applied to detecting minute defects in various curved samples. In addition, the range diagrams that do not depart from the gist of the present invention are for explaining the operation of the above-mentioned apparatus, and FIG. 2 is a characteristic diagram showing the relationship between the distance from the sample to the lens and the intensity of the photoacoustic signal, and FIG. The figure is a characteristic diagram showing the relationship between the sample position and the intensity of the photoacoustic signal.
１１．２１・・・レーザ管、１２．２２・・・メカニカ
ルチョッパ、１３．２３・・・発振器、１４・・・第１
の光ビーム、１５・・・第２の光ビーム、１５．２５・
・・反［，１６，２６・・・集光レンズ、１７．２７・
・・ロックインアンプ、１８・・・集光レンズ制御回路
、１９．２９・・・集光レンズ位置調整機構、２８・・
・レコーダ、３０・・・試料、３１・・・セル、３２・
・・光透過窓、３３・・・マイクロフォン。11.21... Laser tube, 12.22... Mechanical chopper, 13.23... Oscillator, 14... First
Light beam, 15...Second light beam, 15.25.
・・Anti[, 16, 26 ・・Condensing lens, 17.27・
... Lock-in amplifier, 18... Condensing lens control circuit, 19.29... Condensing lens position adjustment mechanism, 28...
・Recorder, 30... Sample, 31... Cell, 32.
...Light transmission window, 33...Microphone.
Claims (4)
、試料から得られる光音響信号を検出して試料の表面若
しくはその直下の欠陥を検出する方法において、異なる
周波数で変調された２本の光ビームを試料表面の近接し
た異なる２点に集光し、第１の光ビームの照射による光
音響信号に基づいて試料表面の高さ変動量を検出し、該
高さ変動量に応じて第２の光ビームが試料表面に微小ス
ポット光として集光するよう調節し、この状態で第２の
光ビームの照射による光音響信号に基づいて前記欠陥検
出を行うことを特徴とする表面欠陥検出方法。(1) In a method of scanning the sample surface with an intensity-modulated light beam and detecting photoacoustic signals obtained from the sample to detect defects on the sample surface or directly below, two beams modulated at different frequencies are used. The light beam is focused on two different points close to each other on the sample surface, and the amount of height variation on the sample surface is detected based on the photoacoustic signal generated by the irradiation with the first light beam. A surface defect detection method characterized in that the second light beam is adjusted so as to be focused on the sample surface as a minute spot light, and in this state, the defect detection is performed based on a photoacoustic signal generated by irradiation with the second light beam. .
表面上のビーム径Ｄ＿１と、前記第２の光ビームの変調
周波数ｆ＿２及び試料表面上のビーム径Ｄ＿２とは、 ｆ＿１＜ｆ＿２ Ｄ＿＞Ｄ＿２ なる関係にあることを特徴とする特許請求の範囲第１項
記載の表面欠陥検出方法。(2) The modulation frequency f_1 of the first light beam and the beam diameter D_1 on the sample surface, and the modulation frequency f_2 of the second light beam and the beam diameter D_2 on the sample surface are f_1<f_2 D_>D_2 The surface defect detection method according to claim 1, characterized in that the relationship is as follows.
［Ｈｚ］以下、前記第２の光ビームの変調周波数ｆ＿２
は５００［Ｈｚ］以上であることを特徴とする特許請求
の範囲第２項記載の表面欠陥検出方法。(3) The modulation frequency f_1 of the first light beam is 100
[Hz] Below, the modulation frequency f_2 of the second light beam
3. The surface defect detection method according to claim 2, wherein the frequency is 500 [Hz] or more.
μｍ］以上、前記第２の光ビームのビーム径Ｄ＿２は５
０［μｍ］以下であることを特徴とする特許請求の範囲
第２項記載の表面欠陥検出方法。(4) The beam diameter D_1 of the first light beam is 100 [
μm], the beam diameter D_2 of the second light beam is 5
3. The surface defect detection method according to claim 2, wherein the surface defect detection method is 0 [μm] or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61173575A JPS6330758A (en) | 1986-07-25 | 1986-07-25 | Detection of surface flaw |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61173575A JPS6330758A (en) | 1986-07-25 | 1986-07-25 | Detection of surface flaw |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6330758A true JPS6330758A (en) | 1988-02-09 |
| JPH0521501B2 JPH0521501B2 (en) | 1993-03-24 |
Family
ID=15963105
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61173575A Granted JPS6330758A (en) | 1986-07-25 | 1986-07-25 | Detection of surface flaw |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6330758A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0236338A (en) * | 1988-07-27 | 1990-02-06 | Hitachi Ltd | Optoacoustic signal detecting device |
| KR101101988B1 (en) * | 2009-02-16 | 2012-01-02 | 연세대학교 산학협력단 | Near scanning photoacoustic apparatus |
| GB2484673A (en) * | 2010-10-18 | 2012-04-25 | Univ Dublin City | A photoacoustic inspection device |
| GB2503722A (en) * | 2012-07-06 | 2014-01-08 | Sonex Metrology Ltd | A photoacoustic inspection device |
| GB2515840A (en) * | 2013-07-04 | 2015-01-07 | Sonex Metrology Ltd | An acoustic isolation chamber |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4251601B2 (en) * | 2001-12-20 | 2009-04-08 | 株式会社東芝 | Laser ultrasonic inspection equipment |
-
1986
- 1986-07-25 JP JP61173575A patent/JPS6330758A/en active Granted
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0236338A (en) * | 1988-07-27 | 1990-02-06 | Hitachi Ltd | Optoacoustic signal detecting device |
| KR101101988B1 (en) * | 2009-02-16 | 2012-01-02 | 연세대학교 산학협력단 | Near scanning photoacoustic apparatus |
| GB2484673A (en) * | 2010-10-18 | 2012-04-25 | Univ Dublin City | A photoacoustic inspection device |
| GB2503722A (en) * | 2012-07-06 | 2014-01-08 | Sonex Metrology Ltd | A photoacoustic inspection device |
| GB2515840A (en) * | 2013-07-04 | 2015-01-07 | Sonex Metrology Ltd | An acoustic isolation chamber |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0521501B2 (en) | 1993-03-24 |
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