| 摘要 |
A filter removes certain noise-induced artifacts from a two-dimensional image of a bore-hole wall, this image being formed by signals from a two-dimensional array of staggered electrodes pulled along the bore-hole wall. The noise artifacts are due to a type of noise which varies as a function of depth of the array, but which is substantially the same at all electrodes at any given time. The artifacts appear in the image in the form of a "footprint" of the electrode array, as an unintended result of a depth-adjustment process in which the original frames of samples of the signals at the electrodes of the staggered array, all taken essentially at the same time, are later resampled to produce frames of samples each corresponding to the same depth in said bore-hole. The filter makes use of the fact that the configuration of the artifact in the image is known, and that the true signal values do not change much between azimuthally adjacent electrodes. The preferred form of the filter produces, and substracts from each sample, a value of noise n which is a function of the depth of each electrode and which is such as to minimize the minimal discontinuity measure.
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