KEYWORDS: Signal processing, Cameras, Video, Field programmable gate arrays, Image processing, Video processing, Solid state cameras, Solids, Microcontrollers, Thermography
The video signal preprocessing unit (processor) for thermovision camera, developed by the authors on the basis of a pyroelectric vidicon, is intended for: calculation of a difference between the `positive' and `negative' frames, obtained in obturation mode; n-divisible accumulation of the resulting frame; non-volatile storage of the received images; images transmission to the computer. These functions are realized by means of following units: video signal digitizer; arithmetic-logical unit; accumulation; display and archive memory units; microcontroller. Processor is developed with Field Programmable Gate Arrays use. Its structure is considered.
Thermovision systems based on the pyroelectric vidicon (PV) are low-cost non-cooled devices for image creation in far infrared range of spectrum. For such systems it is necessary to form the positive pedestal charge to prevent PV from blanking and to decrease electron beam delay. Secondary emission pedestal mode (SEPM) is most frequently used for this purpose. It provides pedestal creation during retrace time of horizontal scanning. This paper is dedicated to examining of the SEPM influence on pyroelectric vidicon focusing and deflection mode changes, analysis results of the influence and finding possible ways to correct them. It is shown that SEPM causes deflection decreasing during retrace raster, performed estimation shows that trace and retrace rasters are considerably different. The trace and retrace rasters matching enables to improve the power parameters of the scanning and to increase target commutation time (sensitivity) and number of active scanning lines (spatial resolution). The methods of the trace and retrace raster matching are discussed. The advantages and shortcomings of these methods are pointed out. An estimation of thermovision system parameters improvement is calculated. The obtained results provide a good basis for designing low- cost portable thermovision systems with improved power parameters, resolution and sensitivity.
KEYWORDS: Digital watermarking, Visualization, Image processing, Digital imaging, System identification, Multimedia, Image acquisition, CRTs, Spatial resolution, Detection and tracking algorithms
This paper presents a new approach for the secure integrity verification of driver licenses, passports or other analogue identification documents. The system embeds (detects) the reference number of the identification document with the DCT watermark technology in (from) the owner photo of the identification document holder. During verification the reference number is extracted and compared with the reference number printed in the identification document. The approach combines optical and digital image processing techniques. The detection system must be able to scan an analogue driver license or passport, convert the image of this document into a digital representation and then apply the watermark verification algorithm to check the payload of the embedded watermark. If the payload of the watermark is identical with the printed visual reference number of the issuer, the verification was successful and the passport or driver license has not been modified. This approach constitutes a new class of application for the watermark technology, which was originally targeted for the copyright protection of digital multimedia data. The presented approach substantially increases the security of the analogue identification documents applied in many European countries.
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