Magnet assembly and a voice coil motor using such magnet assembly

A voice coil motor for controlling the evenness of gap magnetic flux comprising:

• an upper yoke and lower yoke oriented to provide a required clearance;
• a pair of magnet assemblies fixed to the surfaces of the upper yoke and lower yoke facing the clearance, at least one of the pair of magnet assemblies having a circular arc cross-section of two magnet pieces, each magnet piece having a first portion including a first end, a center portion, an opposite second portion including a second end, an inner surface, and an outer surface, the two units abutted to each other at the first end of each unit, one unit having a direction of magnetization from the inner surface toward the outer surface of the unit, the other unit having a direction of magnetization from the outer surface toward the inner surface of the unit, each unit having a magnetic flux density being higher in the first portion than that of the center and the second portion;
• and
• a coil structured to swing through the gap formed between the pair of magnet assemblies.