Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
1999-04-28
2001-08-07
Chapman, John E. (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S597000, C374S119000
Reexamination Certificate
active
06269700
ABSTRACT:
Industry requires contactless dimensional inspection tools for measuring profiles complementing available mechanical and optical tools. When measuring profiles, the surface to be inspected is not always highly optically reflective and the roughness to be measured and the area over which the measurement is to be effected are not always suited to an optical technique. It is not always possible to bring a sample into mechanical contact with a micrometric feeler, simply because the structure to be inspected is too fragile to withstand the stress applied by the feeler.
The present invention proposes contactless means of access to dimensional inspection and even measurement of roughness of optical grade surfaces of widely varying mechanical impedance.
The invention therefore concerns a contactless device for measuring the distance between a surface of a read head consisting of one or more emitters and one or more receivers consisting of electromechanical transducers X coupled to mechanical amplifiers C (FIG.
1
). The probed object ECH (
FIG. 3
) has a different mechanical impedance than the medium in which ultrasound waves generated in the read head propagate. In the present invention, the propagation medium between the probed object and the read head is the air of the atmosphere, but any other gaseous medium could be suitable. The mechanical amplifiers are solid spikes, generally with a conical profile and with a bandwidth adapted to amplify impulse or harmonic ultrasound motion in an antisymmetrical guided mode, for example a bending mode, i.e. a mode whose component of displacement orthogonal to the axis of cylindrical symmetry of the cone is antisymmetrical to that axis. The use of an antisymmetrical mode coupled to a focussing spike has the unique advantage of generating with sufficient localized directional intensity an ultrasound field CHP (
FIG. 2
) directed toward the object to be probed. Measuring the flight time in an impulse mode or the amplitude and phase of the echo reflected from the probed surface in a harmonic mode measures the distance between a surface element SS (
FIG. 8
) of the probed object and the end of the focussing spike.
REFERENCES:
patent: 4281407 (1981-07-01), Tosima
patent: 4594897 (1986-06-01), Bantz
patent: 0045456 (1981-07-01), None
patent: WO96 11378 (1996-04-01), None
RCA Review, vol. 44, No. 3. Sep. 1983, pp. 430-464, “Surface acoustic wave stylus: Part I-Pickup and recording devices,” S. Toshima et al.
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Science, vol. 76A, No. 10, Oct. 1993, “A Noncontact Thickness Measurement of Thin Samples Using 40 kHz Ultrasonic Wave”, K. Imano et al., pp. 1861-1862.
Patent Abstracts of Japan, vol. 009, No. 292 Nov. 19, 1985.
Blakely & Sokoloff, Taylor & Zafman
Chapman John E.
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