We present an endoscopic probe for optical coherence tomography (OCT) equipped with a miniaturized hollow ultrasonic motor that rotates the objective lens and provides an internal channel for the fiber to pass through, enabling 360 deg unobstructed circumferential scanning. This probe has an outer diameter of 1.5 mm, which is ultra-small for motorized probes with an unobstructed view in distal scanning endoscopic OCT. Instead of a mirror or prism, a customized aspheric right-angle lens is utilized, leading to an enlargement of the numerical aperture and thus high transverse resolution. Spectral-domain OCT imaging of bio-tissue and a phantom are demonstrated with resolution of 7.5  μm(axial)×6.6  μm(lateral) and sensitivity of 96 dB.

This article reports a screw-driven polyhedron linear ultrasonic motor (USM) of nut-type. It is comprised of a stator, which is a threaded metal nut bonded with piezoelectric plates on its external surface, and a rotor with external threads, which engage with the internal threads of the stator. A traveling wave in the plane is stimulated on the stator when harmonic electric signals are applied to the piezoelectric plates. The traveling wave drives the rotor to rotate, and the threads transform the rotation into a linear motion. The lens can be fixed in the rotor and realize the integrated design of the auto focus system. This structure can omit retarder and directly drive to obtain a high accuracy of positioning, and it is shockproof. A mini AF cellular phone module (8.5 mm×8.5 mm×5.9 mm) driven by this motor was made and an image resolution of 3-5 MP was obtained in the module prototypes of the cellular phone.ultrasonic motor, nut-type, screw drive, lens AF, modulesThe explosive development of mobile phones makes it more and more necessary to bring auto focus into mobile phones so as to achieve better image quality. Tiny motors with low cost are needed to create auto focus and optical zoom in mobile phones which are far smaller than the digital cameras and can withstand high shock loads. The conventional electromagnetic motors have low efficiency for small sizes, because more and more electrical driving power is converted into heat, rather than mechanical motion [1] . Moreover, they require gear reduction ratio, which has already reached their practical limit of miniaturization.Compared with conventional electromagnetic motors, the ultrasonic motor is a new type of actuator which utilizes the inverse piezoelectric effect of piezoelectric materials to produce vibrations at ultrasonic frequencies. It has many outstanding features, such as low speed, high torque, quick response, self-hold without power, easy miniaturization, and so on.As early as in the 1980s, Canon Inc. had successfully utilized the ultrasonic motors in the focus system of digital cameras and realized the industrialization of ultrasonic motors [2] . Zheng et al. [3] and Yoon [4] developed the small discreteness of lens. In 2005 a named SQUIGGLE motor of New Scale Tech Inc. was 1.55 mm×1.55 mm square and 6 mm long threaded nut, which used the first bending vibration to rotate and drive a threaded screw. It was capable of sub-micrometer stepping and very cheap. However, it was incapable of integrating module with lens.The new nut-type linear ultrasonic motors presented here is developed to meet the requirements of mobile phone [5][6][7] . The excellent characteristics of this motor are:(1) Lens assemblies can be fixed in the screw rotor or nut stator in order to create auto focus or optical zoom and realize the unique operating design of focus system;(2) The thread driving system directly drives the rotation of the rotor into the linear motion without using gears or cams, and thus can obviously reduce the number of components and thereby the cost.

No abstract

No abstract

A new mini-ultrasonic motor with a metal bar and piezoelectric plate hybrid as a stator has been studied. Four piezoelectric plates are bonded to four sides of the metal bar. The metal bar is made of brass and the piezoelectric plates are made of Pb(Zr-Ti)O 3 . The polarization direction is vertical to the piezoelectric plate. Compared with the cylindrical type of motor, the motor with a square cross-section makes polarization more sufficient and the signal wire easier to be welded. In this study, the modal and harmonic analyses of the stator were performed by using the Finite Element Method. The resonance frequency of the motor is about 100 kHz, the no-load revolution is above 6000 rpm and the maximum torque is about 60 mN m. This new miniultrasonic motor has potential applications.