Design and characterization of a thin linear ultrasonic motor for miniature focus systems

Shunsuke Izuhara, Tomoaki Mashimo

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


We present a miniature linear piezoelectric ultrasonic motor with a thin and hollow design, which can serve as an essential component of autofocusing features in next-generation camera modules. It consists of a thin square stator with a hole and an elastic cylindrical slider with a slit. The motor design, in which the slider inserted into the stator hole expands outward, enables a hollow structure for centering a lens and an optimal preload for enhancing the motor thrust force. In this study, we model the relationship between the dimensions and the preload statically to quantify the preload value and clarify the design methodology of the motor. After optimizing the preload empirically, we evaluate the fundamental characteristics experimentally. The stator with a side length of 4.5 mm and a thickness of less than 1 mm provides a thrust force of 12.9 mN that leads to a quick response, which is a requirement of autofocusing. Finally, the motor drive system with visual feedback control is used to demonstrate the positioning of an actual lens group in front of an image sensor to obtain clearer images.

Original languageEnglish
Article number112797
JournalSensors and Actuators, A: Physical
Publication statusPublished - Oct 1 2021
Externally publishedYes


  • Autofocus
  • Micromotors
  • Piezoelectric actuators
  • Ultrasonic motor
  • Visual feedback

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering


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