In order to improve the performance of homomorphic filtering technique for face images, band pass filter is selected to replace the conventional high pass filter in homomorphic filtering technique. Apart from the noise reduction capability, the band pass filter is specifically designed for face images as it is based on the locations of illumination component in Fourier spectrum. The qualitative...

The Fractional Fourier Transform (FRFT) is a generalization of the classical Fourier transform and has many applications in several areas including signal processing, optics and quantum mechanics. This paper presents a low pass filter, designed by using convolution theorem for FRFT. In the design of filter, Blackman window function is used and it has been observed that proposed FRFT domain filt...

Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked f...

The mathematical problem for Electrical Impedance Tomography (EIT) is a highly nonlinear ill-posed inverse problem requiring carefully designed reconstruction procedures to ensure reliable image generation. D-bar methods are based on a rigorous mathematical analysis and provide robust direct reconstructions by using a low-pass filtering of the associated nonlinear Fourier data. Similarly to low...

We report on selection and stabilization of transverse optical patterns in a feedback mirror experiment. Amplitude filtering in the Fourier plane is used to select otherwise unstable spatial patterns. Optical turbulence observed for nonlinearities far above the pattern formation threshold is stabilized by low-pass filtering of the optical power spectrum. Experimental observations obtained with ...

Frequency domain filtering modifies the brightness values of the pixels in the image depending on their periodic patterns and on the spatial distributions of brightness variations in the image. The high pass filters tend to preserve the sharp brightness variation patterns and to remove the smooth variations in the image (along with the DC component, i.e. with the average brightness which is set...

When the short-time Fourier transform (STFT) of an audio signal is arbitrarily modified, it no longer truly represents a time-domain signal. Classically, the accepted solution to obtain a time-domain signal from a modified STFT (MSTFT) is to invert the MSTFT to a time-domain signal that has an STFT that is closest to the MSTFT in a least squares sense. This is also the approach currently taken ...

A small gate array is evolved extrinsically to carry out a low pass filtering task defined over fifteen different frequencies. The circuit is evolved by assessing its response to digitised sine waves. Two different fitness functions are contrasted. One is based on computing the sum of the absolute differences between the actual response and that desired, the other is defined by examining charac...