  We propose a transform theory for calculating a density profile of small
colloids around a large colloid from a force curve between the two-large
colloids. In the colloid solution, there are many small colloids and two or
several large colloids. The force curve between the two-large colloids can be
measured by laser tweezers. In this letter, the transform theory is derived in
detail, where a superposition approximation of the radial distributions of the
density profiles and rigid-body approximation are introduced. In our opinion,
if the experimental condition is satisfied, the transform theory can be used
not only for the laser tweezers, but also for surface force apparatus and
colloid probe atomic force microscopy. Furthermore, the transform theory is to
calculate a density profile of micelles around a large spherical surface.
