Research on real-time measurement and grading method for pearl color

The pearl color and color uniformity are important to its price. The paper presented a new real-time method to measure and grade the pearl color based on optoelectronic techniques. The method uses HSI (Hue, Saturation and Intensity) color model, diffuse reflection illumination, CCD (Charge Couple Device) camera with fine color reproduction and digital image processing technology to realize the parameters of color matrix of pearl color. These parameters, including mean values (h and s), variances (σh and σs) and absolute values of third moments (|th| and |ts|) of H and S, were acquired. Then the industrial control computer acquires the grading signals. The grading devices graded the pearls. The method could measure and grade the pearl on real-time and meet the requirement of grading.