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Polyvinilidene fluoride (PVDF) single-element transducers for high-frequency (>30 MHz) ultrasound imaging applications have been developed using MEMS (Micro-electro-Mechanical Systems) compatible techniques. Performance of these transducers has been investigated by analyzing the sources and effects of on-chip parasitic capacitances on the insertion-loss of the transducers. Modeling and experimental studies showed that on-chip parasitic capacitances degraded the performance of the transducers and an improved method of fabrication was suggested and new devices were built. New devices developed with minimal parasitic effects were shown to improve the performance significantly. A 1-mm aperture PVDF device developed with minimal parasitic effects has resulted in a reduction of insertion loss of 21 dB compared with devices fabricated using a previous method. [ABSTRACT FROM AUTHOR]

Polyvinilidene fluoride (PVDF) single-element transducers for high-frequency (>30 MHz) ultrasound imaging applications have been developed using MEMS (Micro-electro-Mechanical Systems) compatible techniques. Performance of these transducers has been investigated by analyzing the sources and effects of on-chip parasitic capacitances on the insertion-loss of the transducers. Modeling and experimental studies showed that on-chip parasitic capacitances degraded the performance of the transducers and an improved method of fabrication was suggested and new devices were built. New devices developed with minimal parasitic effects were shown to improve the performance significantly. A 1-mm aperture PVDF device developed with minimal parasitic effects has resulted in a reduction of insertion loss of 21 dB compared with devices fabricated using a previous method. [ABSTRACT FROM AUTHOR]

Laser beam drift greatly influences the accuracy of a four degrees of freedom (4-DOF) measurement system during the detection of machine tool errors, especially for long-distance measurement. A novel method was proposed using bellows to serve as a laser beam shield and air pumps to stabilize the refractive index of air. The inner diameter of the bellows and the control mode of the pumps were optimized through theoretical analysis and simulation. An experimental setup was established to verify the feasibility of the method under the temperature interference condition. The results indicated that the position stability of the laser beam spot can be improved by more than 79% under the action of pumping and inflating. The proposed scheme provides a cost-effective method to reduce the laser beam drift, which can be applied to improve the detection accuracy of a 4-DOF measurement system. [ABSTRACT FROM AUTHOR]