A Pitch-variation Moiré Fringes Method of Temporal Phase Unwrapping Profilometry

A method of pitch-variation moiré fringes is proposed to realize the temporal phase unwrapping for three-dimensional profilometry. On the basis of the principle of moiré pattern,we achieve variable spatial frequencies of fringes in a moiré pattern by rotating two gratings. Furthermore a five-point fitting method is used to automatically compute the central position of side-lobe spectrum of the moiré fringes. Finally,a generalized temporal phase unwrapping algorithm is intro-duced to process the three-dimensional reconstruction. The theoretical analysis and experimental results show the validity of the proposed method.

Analysis of detection limit to time-resolved coherent anti-Stokes Raman scattering nanoscopy

In the implementation of CARS nanoscopy, signal strength decreases with focal volume size decreasing. A crucial problem that remains to be solved is whether the reduced signal generated in the suppressed focal volume can be detected. Here reported is a theoretical analysis of detection limit （DL） to time-resolved CARS （T-CARS） nanoscopy based on our proposed additional probe-beam-induced phonon depletion （APIPD） method for the low concentration samples. In order to acquire a detailed shot-noise limited signal-to-noise （SNR） and the involved parameters to evaluate DL, the T-CARS process is described with full quantum theory to estimate the extreme power density levels of the pump and Stokes beams determined by saturation behavior of coherent phonons, which are both actually on the order of ~ 109 W/cm2. When the pump and Stokes intensities reach such values and the total intensity of the excitation beams arrives at a maximum tolerable by most biological samples in a certain suppressed focal volume （40-nm suppressed focal scale in APIPD method）, the DL correspondingly varies with exposure time, for example, DL values are 103 and 102 when exposure times are 20 ms and 200 ms respectively.

All-solid-state microscopic interferometer with frequency-variation and phase-shifting capability

A novel microscopic interferometry with ability of frequency-variation and phase-shifting is proposed for microstructures testing. By using acousto-optic technique, sequential carriers can be generated with different spatial frequencies so that the temporal phase unwrapping method can be applied for decoding the height information. Combined with phase-shifting technique realized by spatial light modulator, this method is especially suitable for interferometric measurement with high precision and large dynamic range.

Flexible multifunctional platform based on piezoelectric acoustics for human–machine interaction and environmental perception

Flexible human–machine interfaces show broad prospects for next-generation flexible or wearable electronics compared with their currently available bulky and rigid counterparts.However,compared to their rigid counterparts,most reported flexible devices(e.g.,flexible loudspeakers and microphones)show inferior performance,mainly due to the nature of their flexibility.Therefore,it is of great significance to improve their performance by developing and optimizing new materials,structures and design methodologies.In this paper,a flexible acoustic platform based on a zinc oxide(ZnO)thin film on an aluminum foil substrate is developed and optimized;this platform can be applied as a loudspeaker,a microphone,or an ambient sensor depending on the selection of its excitation frequencies.When used as a speaker,the proposed structure shows a high sound pressure level(SPL)of~90 dB(with a standard deviation of~3.6 dB),a low total harmonic distortion of~1.41%,and a uniform directivity(with a standard deviation of~4 dB).Its normalized SPL is higher than those of similar devices reported in the recent literature.When used as a microphone,the proposed device shows a precision of 98%for speech recognition,and the measured audio signals show a strong similarity to the original audio signals,demonstrating its equivalent performance compared to a rigid commercial microphone.As a flexible sensor,this device shows a high temperature coefficient of frequency of−289 ppm/K and good performance for respiratory monitoring.