A novel DSPI system for vibration quantificational analysis

Vibration measurement by digital speckle pattern interferometry (DSPI) has the merits of high precision, no-contact and full-field measurement. Because the fringes achieved by the DSPI time-average vibration measurement are Bessel fringes, its quantificational analysis is difficult. The quasi-phase-shifting technique of Bessel fringes is used for the DSPI vibration quantificational analysis. A bias reference vibration at the same frequency is introduced into the reference beam as an object vibration. The Bessel fringes will shift when the phase of the bias reference vibration changes, which is equivalent to the phase-shifting of cosine fringes. So the Bessel fringes of DSPI vibration measurement can be analyzed quantitatively through the phase-shifting algorithm. A novel DSPI system for vibration quantificational analysis is developed. A low voltage phase-stepper and the measurement control electric circuit are designed and fabricated. The vibration testing results of a circumference fixed circular disc and a four-side mixed square copper piece are given. The vibration modality can be measured conveniently through this system, and the quality of the measurement result is good.