This paper presents an enhanced vision system of the "Selective
Stereo Gradient Method" (SSGM). Its purpose is the detection of
topographies of highly reflective, metallic surfaces of quickly
moving metallic tokens. We call this vision system the
3-Color-SSGM. It represents a decisive improvement of the
serial-SSGM. The objective is to decide from comparison of the
measured characteristic surface topography with topographical data
stored in a database whether the token belongs to a reference
class or not. In the improved SSGM a 3 sector 120° color
LED-illumination setup is used for generating a single image of a
moving object. Using the spectral properties of the illumination,
which matches to the special spectral characteristics of the
camera, three independent images can be extracted. The comparison
between these images leads to a discrimination between a real
object with 3D topography and a photographic image. The
experimental setup and special illumination conditions are
described. The raw data images are segmented and scaled. Rotation
and translation invariance of the recognition and classification
process are implemented. A specimen can be classified by using
statistical image analysis and template matching methods. The
classification statistics results will be reported.
This paper presents a vision system whose purpose is to detect topographies of high reflective, metallic surfaces of minted tokens. We call this technique 'Selective Stereo Gradient Method' (SSGM). The objective is to decide whether the token belongs to a reference class or not. The most important property of the SSGM is that the classification can not be deceived by a photographic image and hence yields high fraud protection. To achieve this a 3 sector 120# LED illumination is used for generating three images under different illumination directions. The comparison between these three sequentially taken images leads to a discrimination between a real object with 3 D topography and a photographic image. The experimental setup and special illumination conditions are described. Rotation and translation invariance of the recognition and classification process are implemented. This is achieved by image transformation into a suitable coordinate system. A specimen will be identified to belong to the class of interest if, in a subsequent template matching step, selected patterns taken from the class reference object, can be successfully identified. If a first pattern is found additional patterns will be searched for. The classification statistics results will be reported for metallic tokens.
KEYWORDS: Polymers, Nonlinear optics, Polymer thin films, Near field scanning optical microscopy, Electrodes, Microscopy, Near field optics, Dielectric polarization, Dielectrics, Signal detection
Electric field poling of nonlinear optical (NLO) polymer films at very high electric fields can lead to (chi) (2)- distributions with poor spatial homogeneity, making such films unsuitable for optical devices. We report on further improvements of our scanning second harmonic microscopy using scanning near field optic techniques and on result on scanning optically poled films. Using a scanning Kelvin microprobe, a 2D image of the charge and polarization distribution inside the polymer films can be obtained. Similarities between the charge image and the second harmonic image are observed and allow to analyze the casus of the (chi) (2)-fluctuations. By measuring poling currents through triple stack layers and simultaneously detecting the second harmonic response, the internal electric field inside the NLO-film can be determined. Amorphous SiC:H layers, which were obtained by plasma enhanced chemical vapor deposition, are shown to be suitable for optical buffer layers and for dielectric interface coatings.
We present a novel nondestructive experimental technique for the determination of the lateral distribution of the polar order in second order nonlinear optical (NLO) thin films. The sample, which consists of a poled polymer film, is scanned through the focus of an infrared laser beam in a second harmonic generation (SHG) setup and the second harmonic intensity is monitored stepwise. In combination with a conventional electrooptic (EO) characterization it is possible
to create an EO-coefficient map of the sample. The resolution of this mapping technique can be significantly increased by using high numerical aperture (NA) microscope optics for the illumination of the poled polymer. This method, for instance, allows the evaluation ofpoling inhomogeneities due to high field poling and field distortions at the edges ofpoling electrodes.
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