  This paper provides a simple proof of the mutual incoherence condition $\mu <
\frac{1}{2K-1}$ under which K-sparse signal can be accurately reconstructed
from a small number of linear measurements using the orthogonal matching
pursuit (OMP) algorithm. Our proof, based on mathematical induction, is built
on an observation that the general step of the OMP process is in essence same
as the initial step since the residual is considered as a new measurement
preserving the sparsity level of an input vector.
