We discuss the solution of boundary value problems that arise after the
separation of variables in the Schr\"odinger equation in oblate spheroidal
coordinates. The specificity of these boundary value problems is that the
singular points of the differential equation are outside the region in which
the eigenfunctions are considered. This prevents the construction of
eigenfunctions as a convergent series. To solve this problem, we generalize and
apply the Jaffe transformation. We find the solution of the problem as
trigonometric and power series in the particular case when the charge parameter
is zero. Application of the obtained results to the spectral problem for the
model of a quantum ring in the form of a potential well of a spheroidal shape
is discussed with introducing a potential well of a finite depth.Comment: 5 pages, 3 figures, proc. Days on Diffraction 201