Study on pre-correction method for LED chip declination in sorting system

Chip declination correction is a difficult problem in LED chip sorting process. Usually use real-time vision to correct chip declination. In this way, once correction may need several adjustments. It may cause great reduction for die production rate. Aiming at an effective solution of this problem, a declination pre-correcting method is proposed in this paper. Techniques including least-squares method to fit location of rotation center, computational method of positions to be corrected. Paper also proposed an iterative formula to revise the fitting rotation center position to ensure the accuracy, and discussed the over-quadrant phenomenon in chip declination pre-correction process. Experimental results show that the final deviation which includes image recognition error is less than 12μm. It is acceptable for chip sorting. By contrast with traditional method, pre-correction method needs only one adjustment in most cases, it is more effective and efficient.