Energy calibration of SuperNEMO demonstrator will be performed by 207Bi sources. They were produced in form of point-like droplets deposited between two transparent mylar foils encased by rectangular frame. Deposited 207Bi droplet should be well centered within the rectangular frame in order to avoid uncertainties in the calibration which could have influence on the data quality. Goal of the presented study is to evaluate how well centered the deposited droplet of 207Bi is within the source frame. Study was performed using the Timepix pixel detectors provided by IEAP CTU in Prague. All the measured sources (49 samples) were categorized based on the quality into three quality groups (the best, good, bad). The table of all measurements is provided giving a possibility to choose only the sources of the best quality.