Measuring and testing – Vibration – By mechanical waves
Patent
1995-01-25
1996-09-03
Williams, Hezron E.
Measuring and testing
Vibration
By mechanical waves
382124, 356 71, 73627, G01N 2926, G06K 900
Patent
active
055512950
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for determining the authenticity and/or for identifying the respective spatial structure of a test specimen, particularly the epithelial structure of the skin e.g. of a human finger, whereby this test specimen is placed on a plane or curved surface and is exposed to ultrasonic waves traversing a body contiguous with said surface and the ultrasonic waves reflected and/or backscattered at the test specimen reproduce a different structure in each case of different test specimens and are evaluated.
Such a method is known from German laid open print No. 40 16 105. Definite identification of individuals is possible because the epithelial structures vary significantly from person to person through the specific genetic code and the individual growth phases. In this method the reflected and scattered ultrasonic waves are intercepted by receivers, so that as large a number as possible of receivers is necessary for determining authenticity or identifying accurately. Since these require a corresponding amount of space, the method is unsuited for the authenticity of, for instance, the epthelial structure of a finger to be quickly checked in a cash dispenser, for example. If the number of receivers is reduced so as to make do with the space, sufficient single data can no longer be received to confidently recognize the individuality of the respective epithelial structure according to the finger placed and to distinguish it from another finger.
The object underlying the invention is therefore to provide a method of the kind mentioned at the outset, enabling high resolution of such a structure with moderately priced means, in the minimum of space.
The object is accomplished in that provided in the body is a layer or surface which is transparent to the ultrasonic waves and reflects and/or diffracts electromagnetic waves, that said layer or surface in the body is deformed in a locally different and time-dependent way by the ultrasonic waves according to the form and intensity of the backscattered or diffracted ultrasonic waves, and that said layer is exposed to radiation of electromagnetic waves at an angle, and in the area of the electromagnetic beams reflected and/or diffracted at the angle of emergence the same are intercepted and their change caused by their reflection or diffraction at the layer is evaluated.
The structures in the test specimen, in particular in the epithelial tissue of the human finger, cause a diffraction of the impinging ultrasonic wave when the ultrasonic wavelength is suitably selected. The diffracted, returning ultrasonic wave causes distortions or deformations in the body and on the layer. Since this layer has the property of reflecting or diffracting electromagnetic waves, the deformation structures on the layer can be optically detected. For instance, so-called CCD-arrays with several thousands of detector elements of matrix-like arrangement may be used as detectors, resulting in a high local resolution and high detection sensitivity with detectors available at moderate price.
It is suitable if the wavelength of the ultrasonic source is selected according to the size of the structures to be identified. Diffraction of the ultrasonic wave at the respective structures thereby occurs.
It is suitable if at least one detector is provided for evaluation of the reflected and/or diffracted electromagnetic beam, preferably of the light, and measures over a selected duration.
Through the evaluation within one time slot one obtains a snapshot of the reflected beam, through measurement within successive time slots separate in time one obtains a time-resolved "film" of the dynamically changing, reflected beam.
It is advantageous if the reflecting and/or diffractive layer in the beam path of the ultrasonic waves is arranged approximately perpendicular to the propagation direction of the ultrasonic waves and the electromagnetic waves are reflectively irradiated at the transition between body and reflecting layer.
The measuring system is simplified by the ultrasonic wave wave f
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patent: 4977601 (1990-12-01), Biez
patent: 5224174 (1993-06-01), Schneider
patent: 5241606 (1993-08-01), Horie
patent: 5258922 (1993-11-01), Grill
Finley Rose M.
Williams Hezron E.
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