Method for producing a modulated grating for an optimal reflection spectrum, which grating is a multiple wavelength reflector. The disk has a plurality a plurality servo burst fields, each including a first normal burst field, a first quadrature burst field, a second normal burst fields and a second quadrature burst field. Once the AT level is determined, a preset exercise program is executed. A mirror plate is connected to the hinge via a contact, and the distance between the mirror plate and the hinge is determined according to desired maximum rotation angle of the mirror plate, the optimum gap and pitch between the adjacent micromirrors.