A continuously variable beam expander driven by ultrasonic motors

Low-loss tunable beam collimator and expander assembly with no moving parts using an engineered diffuser and varifocal lenses

In this paper, we present a novel design for a tunable beam collimator. A variable collimator assists in achieving an adaptive size of an output collimated beam. Alternatively, it can also provide an adjustable output beam divergence angle for a noncollimated beam output. Tunable collimators are highly desirable for various applications in testing, engineering, and measurements. Such devices are also useful in providing tunable illumination of samples or targets in microscopes and emulating different target distances for characterizing the performance of camera systems in laboratory settings. The proposed collimator has two distinct advantages: it is light-efficient compared with pinhole-based collimator designs, and it delivers a large range of output beam sizes without involving the mechanical motion of bulk components. These attributes are achieved via the use of an engineered diffuser (in the place of a pinhole) and a pair of large aperture tunable focus lenses, which deliver a tunable magnification to the output collimated beam. In laboratory experiments, we achieve an optical transmission efficiency of 90% for the proposed tunable collimator.

Development of a novel radial-torsional hollow ultrasonic motor and contact interface coating test

A novel miniature radial-torsional hollow ultrasonic motor is proposed in this work, which is mainly composed of a base, a hollow rotor, a stator. One piece of piezoelectric wafer bonded on the bottom face of the stator is used to excite the radial in-plane vibration mode of the outer ring, which is converted into the revolved motion of the inner ring through the connection beams. The revolved motion of the inner ring can drive the rotor pressed on the inner ring to rotate through friction. The finite-element method was performed to verify the working principle of the motor and optimize the key dimensions of the motor. One prototype motor with the appearance size of Φ35 mm × 12 mm and weight of 20.1 g is fabricated and characterized. In addition, Si₃N₄ thin film is coated on the contact interface of the stator by the magnetron sputtering coating machine to improve the output performance of the ultrasonic motor. The experiment results show that the locked-rotor torque of the motor with coated stator can reach 0.42 mN m, which is 55.56 % higher than that of the uncoated motor.

A Dumbbell Shaped Piezoelectric Motor Driven by the First-Order Torsional and the First-Order Flexural Vibrations

A piezoelectric motor driven by the first-order torsional and first-order flexural (T/F) vibrations is designed, fabricated, and tested in this study. The actuating force is generated by the torsional vibration of the dumbbell-shaped vibrator, while the elliptical motion shape is adjusted with the flexural vibration. The rotor, pressed onto the vibrator’s lateral surface, is frictionally driven with the vibrator. Here, the torsional vibration, the shear modes of piezoelectric ceramics, and the driving method may contribute to high torque and high output power. To test the feasibility of our proposal, first, a prototype of the T/F vibrator is built and its vibration properties are explored. As predicted, the torsional and flexural vibrations are excited on the vibrator. Then, the load characteristics of the piezoelectric motor are investigated. The maximal torque, the no-load rotation speed, and maximal output power are 4.3 Nm, 125 r/min, and 16.9 W, respectively. The results imply that using the first-order torsional and the first-order flexural vibrations is a feasible method to achieve high torque and high output power of piezoelectric motors.