Novel Semiconductor Illumination Technique Based on Color Complementation

The light source is a main part in an image acquisition system, and LED light sources have been widely used in this field for their merits of shape flexibility, long service life, high frequency response, rich colors and low cost. In this paper, light emitting mechanism of LEDs and their spectral characteristics are firstly analyzed and the color complementation method in white LED design is introduced; then a novel illumination method based on color complementation is proposed according to rich colors of LEDs, in which high contrast images can be obtained with selective use of different color light sources after color analysis of the imaging object and background. Experimental results in vision inspection of ICs with ball grid array package (BGA) and chip scale package (CSP) show that with the method proposed, ineffective background information of images can be effectively filtered, data volume of images is significantly reduced and consequently the speed and precision of image processing is greatly improved.