JP2005265823A - Linear wave exciting inspection/evaluation apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for nondestructively detecting defects and the existence of the defects on or under the surface of a solid sample. <P>SOLUTION: The means has a function for utilizing an ultrasonic beam and a light beam, exciting linear waves on the surface of the solid sample, scanning it over the surface of the sample, detecting the reflection and a diffusion of the excited waves and quickly determining whether the defects exist on or under the sample and where the defects exist in a uniform structure based on the magnitude of a signal. Visualization is enabled in combination with the CT technique. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus and a method for performing nondestructive inspection and evaluation of defects and non-uniform portions existing on or inside a solid sample.

  Conventionally, in nondestructive inspection and evaluation of defects on a solid sample surface and inside, there have been thermography, potential method, acoustic emission method, visual observation with an optical fiber, and the like. In addition, a method using a linearly converged beam is also known in an ultrasonic microscope, and photoacoustic tomography combined with CT technology has been realized in the field of photoacoustic imaging.

  In non-destructive inspection using an ultrasonic microscope or photoacoustic microscope, measuring by exciting each point with a light source or an ultrasonic beam that converges in a point-like manner takes too much measurement time as an industrial inspection. There was a bottleneck above and it was necessary to solve this problem.

  According to the present invention, in order to shorten the measurement time in the nondestructive inspection using an ultrasonic microscope or a photoacoustic microscope, a light source that is converged in a linear shape or an excitation source that is arranged linearly by generating a wave with an ultrasonic beam. The present invention solves the conventional problems by obtaining a sum obtained by adding a wave generated from one point along a line.

  Conventionally, in CT typified by X-ray CT (Computerized Tomography), for example, a measurement target such as a human body is virtually divided into a dice on a scanning plane, and along the path along which the X-ray beam passes, The sum of the absorption coefficients is obtained from the transmittance.

  The principle of this apparatus and method will be shown in the following mathematical formula by taking a photoacoustic microscope as an example. The number of regions with unknown sample absorption coefficients is divided into N × N. The light absorption coefficient in the element in the i-th row and j-th column in the array is expressed as αi, j. Assume that scanning is performed with a linear beam large enough to irradiate the entire surface of the sample. Since the photoacoustic signal intensity is proportional to the intensity of the incident light beam and the absorption coefficient of the sample, it occurs when the scanning beam irradiates j columns when the linear beam is horizontally scanned in the column direction. The photoacoustic signal can be written as follows using A as a constant.

  Similarly, when the linear beam is vertically scanned in the column direction in accordance with the row direction, the photoacoustic signal generated when the scanning beam irradiates the i row can be expressed by the following equation.

  N sum data obtained by adding N absorption coefficients on a straight line along the beam can be obtained by scanning in one direction. If the direction of scanning with a linear beam is tilted at various angles divided into N between 0 and 180 degrees, a total of NxN data is obtained, which is numerically consistent with the number of unknowns. It will be solved. This is the principle of CT.

  In the ultrasonic microscope, since imaging is performed not by light absorption but by the difference in intensity of reflected ultrasonic waves, the light absorption coefficient αi, j in the above theoretical formula is used as the ultrasonic reflectance Ri, j. Will be replaced with

  In the present invention, based on the principle of CT, only horizontal and vertical scanning is performed on an unknown region of N × N absorption coefficients. If the sample is uniform and there are no internal defects, the signal is constant because the beam absorption of the sample is uniform at any position in the scan. However, when the linear beam is straddling a region having a defect or the like inside, the signal is increased as compared with the surrounding uniform region.

  In the case of the conventional one-point one-point scanning method, since it is not known whether there is a defect or not, the entire region is scanned, and a long measurement time is required. However, if the area where the defect exists is known in advance by horizontal / vertical scanning using this linear beam, even if the apparatus that scans point by point can scan the area that does not need to be measured. Measurement time can be shortened considerably.

  In particular, when it is desired to measure only the presence / absence of defects in a line, a significant reduction in measurement time can be expected.

  As described above, the present invention provides a nondestructive inspection / evaluation apparatus and method capable of promptly detecting a location where a surface or subsurface defect exists or a portion where the properties of a sample are non-uniform by the incidence of light or an ultrasonic beam. It is. Further, the present invention is also a nondestructive inspection / evaluation apparatus and method that can be combined with a point beam irradiation imaging system or can reconstruct an image by a CT technique while using a linear beam.

  As described above, the present invention has an effect of solving a bottleneck that has been difficult in the prior art in detecting the presence or absence of defects on the surface of a solid sample or under the surface and nondestructively the defects themselves.

  The principle of the apparatus and method according to the present invention will be described below with reference to the drawings, taking as an example the case of measuring a defect in a solid sample.

  First, when there is a defect (2) on the surface or inside of the sample (1) as shown in FIG. 1, it is considered that the linear wave source (3) moves in the waterside direction as shown in the figure. Then, the location where the linear wave source (3) is in contact with the defect (2) is represented by two broken lines (A, B) in the projection drawing drawn outside the sample. Between these two broken lines, the signal generated from the sample is larger than the surrounding uniform region. Even in the case of vertical scanning, the signal increases between two broken lines (A ′, B ′) with which the linear wave source (3 ′) is in contact. In this way, instead of scanning the entire surface of the sample by only two horizontal and vertical scans, only the vicinity of the region to be measured (the portion surrounded by the broken lines A and B and the broken lines A ′ and B ′) is scanned. It will be good.

  In addition, when combined with the CT method, a linear wave source that excites a solid sample is attached to a rotary stage or the like, and is summed along the line of the linear wave source that is inclined in various angular directions on the sample surface. After that, the absorption coefficient at each portion can be obtained by numerical calculation using a computer.

  Furthermore, when combining with the CT method, the signal is acquired by exciting the sample with a linear wave source inclined in the middle of the horizontal and vertical angular directions, and later using a computer, What is necessary is just to obtain an absorption coefficient.

  Next, a first embodiment of the invention is shown in FIG. FIG. 2 shows the usage of an ultrasonic beam. A linear ultrasonic beam passes through a piezoelectric element (4) and a cylindrical ultrasonic lens (5) on a solid sample (2) mounted on a driving device (7). (8) is converged. The scanning direction in this case is the horizontal direction indicated by a double arrow.

  Since the ultrasonic imaging system is attached to the rotary stage (6), the direction of the linear ultrasonic beam on the sample surface can be freely changed, and thus the CT method can be applied.

  This device and method is industrial because it can be expected to shorten the measurement time, reduce costs, and increase the applicability on production lines of microscopes and imaging devices that use the acoustic microscope, photoacoustic microscope, and photothermal effect. There is a high possibility of application in the field, especially industrial application.

It is explanatory drawing which shows the principle of this invention. It is explanatory drawing which showed the implementation method of this invention at the time of using an ultrasonic beam. (Example 1)

Explanation of symbols

1 Solid sample 2 Surface or internal defect 3 Linear wave source (during horizontal scanning)
3 'linear wave source (during vertical scanning)
4 Piezoelectric Element 5 Cylindrical Ultrasonic Lens 6 Rotating Stage 7 Drive Device 8 Linear Ultrasonic Beam

Claims (8)

  The solid or sample (1) surface is irradiated linearly with a pulsed or intermittent light beam (2), and a linear heat source is generated on the surface using light absorption in the solid (1). Thermoelastic waves generated in a sample and sound waves generated in a gas or liquid in contact with a solid are detected by a detector such as a piezoelectric element (3) or a microphone (4), and a linear light beam is detected on the surface of the sample. And inspecting the presence or absence of defects or evaluating non-uniformity of sample concentration more quickly than when performing point-like wave excitation point by point from information such as the magnitude and phase change of the generated signal Apparatus and method having the function of:   Pulse generated by a transducer such as a piezoelectric element (3) or an intermittent ultrasonic beam (2) is linearly shaped and converged on the surface of a solid sample (1) by an imaging system such as a cylindrical lens (4). Then, the reflected wave is detected by returning the reflected wave to an electric signal by a transducer such as the piezoelectric element (3) using reflection of the ultrasonic wave incident on the solid (1) on the surface or inside of the solid sample. Presence / absence of defects more quickly than when performing point-by-point wave excitation based on information such as the magnitude and phase change of the signal that is reflected and returned by scanning a linear ultrasonic beam across the sample surface And a method having a function of inspecting a sample or evaluating a non-uniformity of a sample concentration. The solid or sample (1) surface is irradiated linearly with a pulsed or intermittent light beam (2), and a linear heat source is generated on the surface using light absorption in the solid (1). Heat and temperature rise generated in the sample is detected as a physical change such as deflection or interference of the probe light (5) or the intensity of the generated infrared light, and a linear light beam is scanned across the sample surface and generated. An apparatus having a function of inspecting for the presence or absence of defects or evaluating non-uniformity of the sample concentration more quickly than the case where excitation of a point-like wave is performed point by point from information such as the signal magnitude and phase change And methods. The solid or sample (1) surface is irradiated linearly with a pulsed or intermittent light beam (2), and a linear heat source is generated on the surface using light absorption in the solid (1). The heat and temperature rise generated in the sample is detected as a chemical change such as an electrochemical current in the electrolyte surrounding the sample, and a linear light beam is scanned across the sample surface. From such information, an apparatus and method having a function of inspecting for the presence of defects or evaluating the non-uniformity of the sample concentration, etc., more quickly than when performing point-like wave excitation one by one. 5. A laser beam used as a light beam, an optical system incorporating a function of a microscope, or an optical fiber (12 ′) and movement of a detection unit, and a driving device are used. The apparatus and method according to any one of the above. It corresponds to any one of claims 1 to 5 by a light beam or an ultrasonic beam, and by using a CT (Computed Tomography) method together, it is possible to quickly detect defects and non-uniform portions, The apparatus according to any one of claims 1 to 5, wherein imaging similar to the case where excitation of a point-like wave is performed point by point by rotating the direction of the beam is possible. And methods. An imaging system that corresponds to any one of claims 1 to 5 and that can excite a point-like wave by a light beam or an ultrasonic beam is mounted, and a cylindrical lens to a normal lens is mounted. 2. An imaging system that forms not only a linear beam but also a point-by-point image formation on a sample surface can be used by switching an imaging system such as switching. The apparatus and method in any one of -5. 8. An imaging system using a light beam and an imaging system using an ultrasonic beam, and having a function of switching both ultrasonic measurement and light measurement by switching. The apparatus and method according to any one of the above.

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