The Brightness And Chroma Uniformity Measurement For LED Display Screen Using CCD Camera

In our daily life, LED display screen has been widely used in many areas, such asindoor display, outdoor advertisements, concerts and so on. Among the factorsaffecting display quality of a LED display screen, parameters including chroma andbrightness uniformity are the most important ones. How to measure and evaluate thebrightness uniformity and the chroma uniformity objectively and efficiently is aimportant technique to the development of the uniformity evaluation.In the brightness uniformity aspect, this paper firstly introduces the measurementprinciples of CCD camera and the application of the LED display measured by CCDcamera. From the relationship between LED pixel brightness data and the gray valuesof the photosensitive element, after the distinction of the target and background regions,the brightness on the target regions was extracted exactly. On the basis of those data, ahistogram of the LED pixel is fitted by Gaussian curve. The brightness uniformity isevaluated by standard deviation.In the chroma uniformity aspect, this paper choose L*u*v*color space to evaluatethe uniformity. By converting the RGB color space to the L*u*v*color space,the(u*,v*) coordinates of LED pixels are utilized to fit Gaussian curve. The standarddeviation and mean value of the curve are used to represent the chroma uniformity.The experiment result showed that the evaluation of the brightness uniformity andthe chroma uniformity based on CCD is proved to be fitted with subjective method.Compared with the traditional method, this method is valid and effective.