Color mixture of fluorescent powder is one of the main factors which influence the certified product ratio in color picture tube production. In this paper

the factors causing color mixture are analyzed. The four types of color mixture

i.e. green fluorescent powder remainder

deviation

cover and grain

are analyzed and simulated on computer. Then

a color mixture detecting algorithm of flourescent powder based on the searching with direction array is proposed. Finally

simulation results on DPS-8/52 computer system show that the proposed algorithm has the advantages of high correct detecting probability

strong antinoise ability and high speed.