Moire´ magnification can be observed visually if an array of identical objects is viewed through an array of identical microlenses with a different period. Theoretical analysis and experimental results of the moire´ image obtained by a moire´ magnifier are presented. Conditions for erect and inverted moire´ magnifications are derived and interpreted. Virtual erect images are observed only when the period of the lens array is larger than that of the object array, while inverted images are obtainable in both cases. For equal periods, a uniform field of view results. The relation between the relative size of the periods and the distance between the object and the lens arrays are derived. Expressions for image magnification, orientation and size are deduced. The condition to obtain a demagnified moire´ pattern is deduced. Rotation of the lens array with respect to the object array results in rotation of the erect and inverted moire´ patterns in similar and opposite directions, respectively. © 1998 Society of Photo-Optical Instrumentation Engineers.