This paper presents an efficient image encryption scheme for color images based on quantum chaotic systems. In this scheme, a new substitution/confusion scheme is achieved based on toral automorphism in integer wavelet transform by scrambling only the Y (Luminance) component of low frequency subband. Then, a chaotic stream encryption scheme is accomplished by generating an intermediate chaotic key stream image with the help of quantum chaotic system. Simulation results justify the feasibility of the proposed scheme in color image encryption purpose.
The image preprocessing plays an important role in finger vein recognition system. However, previous preprocessing schemes remind weakness to be resolved for the high finger vein recongtion performance. In this paper, we propose a new finger vein preprocessing that includes finger region localization, alignment, finger vein ROI segmentation and enhancement. The experimental results show that the proposed scheme is capable of enhancing the quality of finger vein image effectively and reliably.
In recent years, verification based on thermal face images has been extensively studied because of its invariance to illumination and immunity to forgery. However, most of them have not given full consideration to high-verification performance and singular within-class scatter matrix problems. We propose a novel thermal face verification algorithm, which is named two-directional two-dimensional modified Fisher principal component analysis. First, two-dimensional principal component analysis (2-DPCA) is utilized to extract the optimal projective vector in the row direction. Then, 2-D modified Fisher linear discriminant analysis is implemented to overcome the singular within-class scatter matrix problem of the 2-DPCA space in the column direction. Comparative experiments on the natural visible and infrared facial expression thermal face subdatabase demonstrate that the proposed approach outperforms state-of-the-art methods in terms of verification performance.
GRIN medium with a lateral sech refractive index variation, can make normal-incident light beam gradually
curve to the medium with a larger refractive index, and periodically converge the light beam to a point smoothly
and continuously. This property of GRIN medium can be used as a coupl er to realize a mode spot size
conversion. This paper mainly discussed the transmission property of Gaussian light beam in a sech GRIN
medium by numerical simulation. SOI waveguide is widely used in the photonic integrated circuit. To achieve a
higher coupling efficiency between single mode optical fiber and single mode SOI slab waveguide, which suffer
a great light beam coupling loss for the mismatch of the spot size. The GRIN medium coupling structures are
designed as a coupler, with symmetric refractive index distribution and asymmetric refractive index distribution.
The insertion loss calculated in theory are 0.71dB and 1.35dB respectively, which has a significant improvement
in coupling loss, compared with the 30dB coupling loss caused by direct butt -joint transmission.
Iris location plays an important role in iris recognition system. Traditional iris location methods based on canny
operator and integro-differential operator are affected by reflections, illumination inconsistency and eyelash. In this
paper, we introduce an accurate iris location method for low quality iris images. First, a reflection removal method is
used to interpolate the specular reflection. Then, we utilize Probable boundary (Pb) edge detection operator to detect
papillary boundary with a lower interference point. Moreover, we optimize the Hough transform to obtain high accuracy
result. Experimental results demonstrate that the location results of the proposed method are more accurate than other