Characterizing opto-electret based paper speakers by using a real-time projection Moiré metrology system

Advancement of distributed piezo-electret sensors and actuators facilitates various smart systems development, which include paper speakers, opto-piezo/electret bio-chips, etc. The array-based loudspeaker system possess several advantages over conventional coil speakers, such as light-weightness, flexibility, low power consumption, directivity, etc. With the understanding that the performance of the large-area piezo-electret loudspeakers or even the microfluidic biochip transport behavior could be tailored by changing their dynamic behaviors, a full-field real-time high-resolution non-contact metrology system was developed. In this paper, influence of the resonance modes and the transient vibrations of an arraybased loudspeaker system on the acoustic effect were measured by using a real-time projection moire metrology system and microphones. To make the paper speaker even more versatile, we combine the photosensitive material TiOPc into the original electret loudspeaker. The vibration of this newly developed opto-electret loudspeaker could be manipulated by illuminating different light-intensity patterns. Trying to facilitate the tailoring process of the opto-electret loudspeaker, projection moire was adopted to measure its vibration. By recording the projected fringes which are modulated by the contours of the testing sample, the phase unwrapping algorithm can give us a continuous phase distribution which is proportional to the object height variations. With the aid of the projection moire metrology system, the vibrations associated with each distinctive light pattern could be characterized. Therefore, we expect that the overall acoustic performance could be improved by finding the suitable illuminating patterns. In this manuscript, the system performance of the projection moire and the optoelectret paper speakers were cross-examined and verified by the experimental results obtained.