Thermal measuring and testing – Temperature measurement – In spaced noncontact relationship to specimen
Patent
1984-07-20
1985-12-10
Frankfort, Charles
Thermal measuring and testing
Temperature measurement
In spaced noncontact relationship to specimen
374124, 374130, G01J 500
Patent
active
045576076
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and a device for the structural, superficial and deep analysis of a body.
For the monitoring of manufacture and the testing of workpieces it is frequently necessary to measure thicknesses of material and determine the superficial and inner structures, for instance, of internal holes or shrinkage cavities in solids.
In order to determine surface structures and check bodies of transparent material optical measuring and testing methods are employed. The examination of structures below the surface of the body as well as contact-free thickness measurements require a large expense when the test pieces consist of bodies of opaque material, for instance metal or a semiconductor. For such examinations ultrasonic or X-ray methods have been generally used up to now. The ultrasonic methods do not operate without contact and are therefore not suitable for the direct continuous examination of moving parts such as, for instance, the examination of rolled plates. Although X-ray methods do not require contact with the material, they are only of limited use, however, for the detection of interface structures.
Devices are also already known which operate in accordance with the so-called opto- (or photo-) acoustic method and which serve for the detection of material structures even below the surface of the material. In the opto-acoustical method local temperature modulation is produced on the surface of the solid to be examined by an intensity-modulated beam of light due to the periodic feeding of heat caused by absorption, said temperature modulation being dependent in amplitude and phase on the removal of heat within the solid.
If the solid is arranged in a hermetically closed chamber, its temperature modulation can be measured by a microphone arranged within the chamber. Since the temperature modulation of the solid goes hand-in-hand with a corresponding modulation of its extent, it can be measured also with a piezoelectric receiver which is firmly connected to the body to be examined. A photo-acoustic microscope which operates in accordance with this principle is known from U.S. Pat. No. 4,255,971. This microscope serves to produce an image of the test piece which is displaced for this purpose with respect to the stationary beam of light.
In both known methods for the opto-acoustical production of a signal, structures within the body to be examined can be imaged via the phase of the measurement signal.
It can readily be seen that in the known methods for the production of an opto-acoustical measurement signal the actual measurement or imaging is limited to a very small range of depth limited by the depth of thermal penetration of the beam of light. The depth of thermal penetration in the case of a test piece of aluminum with a modulation frequency of the beam of light of 20 Hz is only 0.12 cm. Furthermore, these methods require physical contact between the receiver and the sample and are therefore limited to the measurement of small bodies.
BRIEF STATEMENT OF THE INVENTION
The object of the present invention is to provide an opto-acoustical method which permits structural analysis of surface and depth, even on bodies of large diameter and on moving parts, without the range of depth which can be covered being limited by the depth of thermal penetration of the modulated excitation beam.
Starting from the known method in which the body to be examined is scanned with a focused modulated excitation beam and the temperature modulation of the body which is locally induced thereby is measured, this object is achieved by measuring, on the side of the body facing away from the impinging excitation beam, the modulated infrared radiation which proceeds from it. Therefore, only the transmitted heat wave is detected. The signal produced by it is present as an alternating signal which can be electronically processed in simple fashion.
The excitation beam may consist of electromagnetic radiation, for instance light, of electrons or else of ions. In each case an electromagnetic or corpuscular r
REFERENCES:
patent: 3206603 (1965-09-01), Mauro
patent: 3210546 (1965-10-01), Perron
patent: 3287556 (1966-11-01), Good
patent: 3681970 (1972-08-01), Wells
patent: 3805073 (1974-04-01), Jayachandra et al.
patent: 3808439 (1974-04-01), Renius
patent: 3842277 (1974-10-01), Jayachandra
patent: 4041313 (1977-08-01), Potter et al.
patent: 4158772 (1979-06-01), Reedy
patent: 4255971 (1981-03-01), Rosencwaig
patent: 4267732 (1981-05-01), Quate
IBM Technical Disclosure Bulletin, vol. 19, No. 1, Jun. 1976 (New York, U.S.), K. Mueller u.a., `Emission Spectrophotometer`, see pp. 303-304.
Solid State Technology, vol. 18, No. 8, Aug. 1975, (New York, U.S.) H. Matare, `Wafer Testing`, pp. 58-62, see pp. 59-61 cited in the application.
Photoacoustic and Photothermal Spectroscopy, Svein Otto Kanstad & Phys. Technol., vol. II, 1980 (Gr. Britain), Per-Erik Nordal.
"Materials Evaluation", Thermal Surface Impedance Method for Nondestructive Testing by Green, Oct. 1967.
"Solid State Technology", Thermal-Wave Microscopy by Rosencwaig, Mar. 1982.
High Speed Thermal Image Transducer for Practical NDT Applications by Green, May 1970.
Depth-Profiling and Thickness Measurement by Rosencwaig 1980.
Carl-Zeiss-Stiftung Heidenheim/Brenz
Frankfort Charles
Schuster David R.
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