not moving during nonuse and a slow flashing light when iron 100 is not against surface 116 during liftoff sensor chip 206 captures surface images sequentially and uses common features in these image to determine the movement of iron 100 sensor chip 206 writes the x and y displacements over surface 116 in registers delta_x and delta_y respectively sensor chip 206 also tracks the number of visible features in the surface images in order to detect liftoff of iron 100 from surface 116 a high number of visible features indicates that iron 100 is flat against surface 116 so that sensor chip 206 is receiving in focus images on the other hand a low number of visible features indicates the iron is lifted away from surface 116 so that sensor chip 206 is receiving out of focus images sensor chip 206 writes the number of visible features in a register squal surface quality microcontroller 112 is coupled to sensor 114 to read the values in registers delta_x delta_y and squal note that when light source is also used as an indicator microcontroller 112 should only read the values in these registers when the light is on because the values are invalid when the light is off fig3 illustrates a flowchart of.