Quantitative Description of the Quality of Daylight Electroluminescense (dEL) Images Against Dark Room EL Images

We present a robust comparison between Electroluminescence and daylight Electroluminescence images taken with an InGaAs camera, and “golden images” taken under optimal conditions with a Si camera in the dark, which serve as the benchmark. We study the data quality between EL/dEL correlated with the golden images. A key contribution of this work is the correlation of the SNR25 metric, with a pixel-by-pixel mathematical metric called the Similarity Index (SI) which is used to assess image similarity. We compare the similarity between a high-resolution dark EL image of a panel and a dark EL image taken with a low resolution InGaAs camera and quantify the differences showing that there are more complex than a simple resolution degradation. Then, we compare daylight EL images taken at very short exposure times with the high-resolution dark room image. We found that the SNR25 metric correlates well with the SI, allowing us to use this metric as a proxy to assess the quality of the dEL images taken on the field. The results of this research help validate the use of dEL imaging for practical applications, paving the way to define clear cut-offs for minimum quality when using this technique in the field.