The ideal drive current for a little spot is NOT the same as the ideal drive current for a big spot! The reason is that the smallest spot, measuring about 3 microns by 5 microns, is small compared with the 40 micron thickness of the peel sheet and the 180 micron thickness of the base sheet. Heat will therefore flow out of it in three dimensions, as from a point. But when the small laser is kept on for a longer time, to print a spot 5 microns by perhaps 40 microns or 60 microns, the heat flow is from a linear region, and it can only escape in two dimensions. (That is, there is no net heat loss along the line of the heated track.) We can make the drive power optimum for all cases with the small laser spots if we always drop the power to about 2/3 level after printing an exposure track of about 12 microns, as illustrated. Switching times have to be in nanoseconds because the thermal material is being printed at more than 50 miles per hour! With this fix we got rid of a printing problem called "mottle" in the dense regions caused by errors in the autofocus mechanism. 101