[en] Full text: Digital Speckle Pattern Interferometry (DSPI) is widely used and provides high-speed measurements for academic and industrial research. Characterized by simple optical setup and full digital data acquisition and -processing, it provides some advantages to holography which is still bound to wet photo processing. The main drawbacks of DSPI are the grainy structure of the interferograms and the related inherent noise which imposes high demands to evaluation software. Though DSPI is utilized mainly for measurements of mechanical stress and vibration, it can also be used for refractive index measurement in phase objects. With experience in plasma diagnostics by classic and holographic interferometry, we also applied DSPI in this field of research for a more industrial oriented approach. Measurements to determine number densities include 2-wavelength interferometry for electrons and resonant interferometry for heavy particles. The resonant measurement requires a tomographic reconstruction procedure to obtain spatially resolved data from a cross-section of the plasma. The presentation shows the specific implementation of DSPI and assesses its performance within this demanding experimental environment. (author)