释义 |
ConvolutionA convolution is an integral which expresses the amount of overlap of one function as it is shifted over anotherfunction . It therefore ``blends'' one function with another. For example, in synthesis imaging, the measured Dirty Map is a convolution of the ``true'' CLEAN Map with theDirty Beam (the Fourier Transform of the sampling distribution). The convolution is sometimes also known byits German name, Faltung (``folding''). A convolution over a finite range is givenby
 | (1) |
where the symbol (occasionally also written as ) denotes convolution of and . Convolution is moreoften taken over an infinite range,
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Let , , and be arbitrary functions and a constant. Convolution has the following properties:
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 | (4) |
 | (5) |
 | (6) |
The Integral identity
 | (7) |
also gives a convolution. Taking the Derivative of a convolution gives
 | (8) |
The Area under a convolution is the product of areas under the factors,
The horizontal Centroids add
 | (10) |
as do the Variances
 | (11) |
where
 | (12) |
See also Autocorrelation, Convolution Theorem, Cross-Correlation,Wiener-Khintchine Theorem References
ConvolutionBracewell, R. ``Convolution.'' Ch. 3 in The Fourier Transform and Its Applications. New York: McGraw-Hill, pp. 25-50, 1965. Hirschman, I. I. and Widder, D. V. The Convolution Transform. Princeton, NJ: Princeton University Press, 1955. Morse, P. M. and Feshbach, H. Methods of Theoretical Physics, Part I. New York: McGraw-Hill, pp. 464-465, 1953. Press, W. H.; Flannery, B. P.; Teukolsky, S. A.; and Vetterling, W. T. ``Convolution and Deconvolution Using the FFT.'' §13.1 in Numerical Recipes in FORTRAN: The Art of Scientific Computing, 2nd ed. Cambridge, England: Cambridge University Press, pp. 531-537, 1992.
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