Accurate counting techniques are particularly useful to manufacturers of optical compact discs, who need to determine the number of discs packaged in a stack of discs prior to shipment. Manufacturers have tried various techniques, including simply measuring the height of a stack of discs.
Each optical disc is manufactured to a certain thickness, plus or minus a certain tolerance. When many of these discs are stacked on top of each other the cumulative tolerance can easily constitute more than one disc. Due to this large, cumulative tolerance, linear measuring techniques do not yield an accurate count of the number of discs in a stack.
Another technique manufacturers have used is weighing the stack of discs. Apparently, the variation in the weight of each disc is not as significant as the variance in thickness. Therefore, although some variation exists in the weight of each disc, manufacturers can achieve a more accurate, albeit not completely certain, count.
However, the commercially practical weight tolerances create some uncertainty in the result, so a manufacturer cannot achieve a completely accurate count through weighing techniques. As a result, a need exists for a more accurate, automated method for counting optical discs.