In this paper, we first approximate the Gaussian function with any sca
le by the linear finite combination of Gaussian functions with dyadic
scale; consequently, the scale space can be constructed much more effi
ciently: we only perform smoothing at these dyadic scales and the smoo
thed signals at other scales can be found by calculating linear combin
ations of these discrete scale signals. We show that the approximation
error is so small that our approach can be used in most of the comput
er vision fields. We analyse the behavior of zero-crossing (ZC) across
scales and show that features at any scale can be found efficiently b
y tracking from the dyadic scales, thus we show that the new represent
ation is necessary and complete. In the case that the derivatives are
calculated by a special multiscale filter, we show that all the deriva
tive signals can be treated in the same way. Copyright (C) 1997 Patter
n Recognition Society.