PubMed · 3199903
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N R Malik, G Huang. 1988. Integer filters for image processing.. https://doi.org/10.1007/bf02441830
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Acousto-optic tunable filter (AOTF) is an electronically driven dispersive device which operates on the principle of acousto-optic interaction in an anisotropic medium. Incident white light will be diffracted by the AOTF into a specific wavelength when a specific rf is applied to it. The diffracted light needs not be a monochromatic light. Multiwavelength light can be diffracted from the AOTF when several rf signals are simultaneously applied into the filter. Compared to conventional polychromators, advantages of this electronic AOTF polychromator include its ability to individually amplitude-modulate each wavelength of the diffracted multiwavelength light at different frequency. This is accomplished by individually and sinusoidally modulating each applied rf signal at the desired frequency. This feature makes it possible to develop a novel AOTF-based multidimensional fluorimeter in which the sample was simultaneously excited by two different wavelengths (514.5 and 488.0 nm) whose amplitudes were sinusoidally modulated at two different frequencies (100 and 66 Hz). Multicomponent samples, e.g., mixtures of rhodamine 6G and rhodamine B, were successfully analyzed using this novel fluorimeter and the developed data analysis.
In membrane microfiltration of colloidal and cellular suspensions tangential feed ensures continuous operation. Neglecting diffusion (Pe much greater than 1) the purely convective approach predicts well observed dependences between technological parameters and solves the so called microfiltration paradox.
Early stages of visual form processing were modelled by simulating cortical simple, complex and end-stopped cells. The computation involves (1) convolution of the image with even and odd symmetrical orientation selective filters (S-operators), (2) combination of even and odd filter outputs to a local energy measure (C-operator), (3) "differentiation" of the C-operator maps along the respective orientation (single and double end-stopped operators) and (4) determination of local maxima ("key-points") of the combined end-stopped operator activity. While S- and C-operators are optimised for the representation of 1-D features such as edges and lines, the end-stopped operator responses at the key-points make explicit 2-D signal variations such as line ends, corners and segments of strong curvature. The theoretical need for this complementary representation is discussed. The model was tested on grey-valued images.