Electro Optical Techniques (EOP : Electro Optical Probing and EOFM : Electro Optical Frequency Mapping) are effective backside contactless methods for defect localization and design debug for VLSI. The image mode (EOFM) gives only one frequency at each scan. In this case, the frequency mapping is a long and hard task. Furthermore, temporal information is not included in EOFM mode. Building a map by point by point EOP is usually too long so it cannot be used as it is to extract all the frequencies of interest in a region of interest. To overcome this limitation, we have developped an automatic process using EOP mode with a wavelets approach and autocorrelation. Temporal and frequency information are simultaneously computed with only one acquisition. We will underline the challenge and define application boundaries of this technique.