. . . "Since the moveable sub-grating 210 can be suspended by a plurality of springs as shown in FIGS. 6 and 11, a lateral or vertical movement of the sub-grating 210 can be directly related to an acceleration component in a direction of movement of the sub-grating 210 (i.e., F=???kx=mA so that A=???kx/m where k is a spring constant, x is a displacement of the moveable sub-grating 210 in response to a se" .