Abstract: An accurate count and size recognition system of steel balls is developed in order to solve the problems
of inaccuracy of steel balls weighting and counting，steel balls spherical bruises，mixed balls during bearing steel
balls production process． A CCD ( Charge Coupled Device) camera is used in this system to get the images of the
steel balls in the counting-plate，to calculate the quantity of the steel balls and recognize the steel balls of abnormal
size． The system is composed of a feeding channel，an estimated count plate，an accurate count plate，a CCD
camera，a single ball compensating device and a computer etc． The steel balls scroll to the estimated count plate
through the feeding channel and they are arranged in one layer． The area of the estimated count plate can be
adjusted according to the dimension and quantity of the steel balls． The aim of the adjustment is to ensure that the
number of the steel balls on the estimated count plate is less than that of required． The steel balls will enter the
accurate count plate after estimated counting． The steel balls images are captured by the CCD camera which is set
above the accurate count plate． Then binarization is performed to get the binary images of the steel balls，and the
double gray threshold algorithm is adopted to calculate the number of the steel balls． The single ball compensating
device is used to compensate the number difference between the accurate counting and the number of being needed． The steel balls of abnormal size are recognized through comparing the distances between the center of two
neighboring steel balls in a defined district of the accurate count plate one by one． According to the experiments of
the prototype，the system can be used to count steel balls whose diameter are between 4． 763 mm and 25． 4 mm，
the accuracy of counting and the determine rate of the abnormal size steel balls of this system are all up to 100%．

Key words: steel balls count, image processing, size recognition