  The measuring process is studied, where a macroscopic number N of particles
in the detector interact with the object. The macrovariable accompanies the
stationary phase in the path-integral form, which is in one-to-one
correspondence with the eigen-value of the object operator O to be measured.
When N goes to infinity, the fluctuation of the object between different
eigenvalues of O is suppressed, frozen to one the same state while the detector
is on. A model is studied which produces the ideal result when N is infinite,
and the correction terms are calculated in powers of 1/N. It is identical to
the expansion including the fluctuation of the object successively.
