Automatic background brightness control device for colour sorting apparatus.

摘要

The invention relates to an automatic background brightness control device for colour sorting apparatus having a plurality of sorting channels (Q1 - Qn), each including a sensor (S1 - Sn) to detect the amount of reflected and/or transmitted light from objects to be sorted and the amount of reflected and/or transmitted light from a background provided at the sorting channel. A scanner circuit means (12,14, 16) selects from the sorting channels one sorting channel of which the background brightness is to be controlled. A process control means (11) is provided to compare the output from the sensor against a predetermined reference voltages and to produce a signal for controlling the background brightness only when the output from the sensor deviates from the reference voltages. A light control means (P1 - Pn) controls the background brightness within the selected sorting channel according to the signal for controlling the background brightness.