We demonstrate that by appropriately exciting the multistability of the cascaded nonlinear cavities, a broad-bandwidth, reversible, and high-contrast-ratio optical diode can be achieved.
A multi-scale wavelet edge detection algorithm based on directional derivative which can be self-adjusted is proposed.
The high precision and the excellent immunity from noise are achieved. The standard methods of wavelet transform
images along horizontal and vertical directions and suit the detection of horizontal or vertical edges. If they are used to
detect slanting edges, the precision will decline. Other existing wavelet algorithms considering direction information can
only process images along some specified directions. The difficulty confronted by these methods is the dilemma between
the calculational complexity and the orientation accuracy. In this paper, the approach of wavelet edge detection based on
directional derivative which can self-adopt orientation according to edge direction is investigated. The wavelet
transforms are carried out on three scales. At each point of an image, the directional derivative is designed locally based
on the computational results of the neighboring scale so as to acquire self-adjusting characteristic. This has the advantage
to improve precision, and almost not increase the complexity. Besides, the relationship between the Lipschitz exponent
and the magnitudes of wavelet transformation is used to restrain noise. Finally the edge detection experiments for
noise-stained images were done. The results show that our method can achieve both good visual quality and high PSNR
which is enhanced by 3.6 and 6.6 percent respectively comparing with two other wavelet algorithms.
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