On the reconstruction of magnetic source in cylindrical permanent magnets

Abstract

Cylindrical permanent magnets, called magnetic rollers, play a crucial role in copy machines and laser printers. The magnetic roller attracts toner particles by magnetic force and transfers them by its rotational motion to the development zone. It is known that the quality of printed images sensitively depends on the magnetization distribution in the magnetic roller. The numerical analysis of the magnetic fields around the magnetic roller provides useful information for understanding of the motion of toner particles. This chapter describes reconstruction of magnetization distribution in a cylindrical permanent magnet from the magnetic fields measured outside the magnet. The inverse problem is solved by two approaches, one of which is the Tikhonov regularization with the L-curve method for the determination of the regularization parameter. Another approach is based on the conjugate gradient (CG) method, which solves the ill-conditioned linear system without regularization.