METHOD OF READING CLOSED DOCUMENTS Russian patent published in 2012 - IPC G01N29/04 

FIELD: physics.

SUBSTANCE: microscopic ultrasonic "scanning" is performed over a paper medium with the text or graphic information of interest which is protected coatings which are not transparent in the visible range, with further display of the information of interest on a personal computer display, wherein the layer of interest in the paper medium is "scanned" with pulses of linearly frequency-modulated ultrasonic vibrations with a high value of the product of the spectrum width of such a pulsed signal with its duration value, and signals passing through the "scanned" paper medium and received by a piezoelectric sensor undergo spectral-time "compression" in a matched filter on a dispersive delay line, after which the obtained ultra-short radio pulse, after its amplification and amplitude detection, undergoes threshold base limiting, the limiting threshold of which is automatically set based on the control signal from a personal computer so as to eliminate noise signals, after which the obtained useful pulse signals are compared on amplitude with a reference signal, the value of which is determined from the response signal from a threshold device, corresponding to those areas of the paper medium which are known not contain elements of text or graphic information in the layer of the paper medium of interest, but contain a quasi-uniform protective coating, wherein the selected acoustic receiving-transmitting optical system has short focal distance which ensures minimum dimensions of the Airy disc in the combined focal plane of both acoustic lenses, which is combined with the plane of the layer of the paper medium of interest.

EFFECT: high accuracy of reading closed documents.

8 dwg