Automatic background brightness control device for color sorting apparatus

Claim 1

An automatic background brightness control device for colour sorting apparatus having a plurality of sorting channels, each of said channels comprising a sensor, an ejector driver circuit and a feeder, said sensor being adapted 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, said device comprising: a process control means comprising a means for comparing the number of pulses sent from said ejector driver circuit within a predetermined period of time against predetermined reference numbers representative of a decreased grain flow and a normal grain flow and producing feeder control signals for decreasing and increasing the grain flow from said feeder as a result of said comparison to said predetermined reference numbers, respectively, means for comparing outputs from said sensor against predetermined reference voltages while the grain flow is decreased responsive to said feeder control signals and producing a background brightness control signal only when said output from said sensor deviates from said reference voltages, and means for producing a selection signal while the grain flow is normal; a scanner circuit means for selecting, in response to the selection signal from said process control means, from said sorting channels the sorting channel of which the background brightness is to be controlled, said scanner circuit means selecting said sorting channels one after another so that the control of the background brightness of one sorting channel begins upon the completeion of the control of the background brightness of the previous channel; and a light control means for controlling the background brightness within said selected sorting channel according to said background brightness control signal.