A mobile auto-focus actuator based on a rotary VCM with the zero holding current

Area of Science:

• Optics and Photonics
• Mechanical Engineering
• Materials Science

Background:

• Mobile phone cameras require compact and efficient auto-focus systems.
• Existing voice coil motor (VCM) actuators face challenges in power consumption and size reduction.
• The need for precise linear motion from rotational VCMs in miniaturized devices.

Purpose of the Study:

• To develop a novel auto-focus actuator for mobile phone cameras using a rotary VCM.
• To implement an inclined cam mechanism for efficient conversion of rotational to linear motion.
• To achieve zero holding current and reduced module thickness in the focusing lens system.

Main Methods:

• Application of a rotary voice coil motor (VCM).
• Integration of a novel inclined cam structure for motion conversion.
• Theoretical analysis and optimal design of the VCM actuator, cam structure, and preload spring.

Main Results:

• A prototype auto-focus module was manufactured with dimensions of 9.9x9.9x5.9 mm³.
• The developed design enables zero holding current for maintaining focus position.
• Experimental results validated theoretical predictions, meeting mobile camera specifications.

Conclusions:

• The rotary VCM with an inclined cam structure is a viable solution for mobile camera auto-focus.
• The design offers significant advantages in power efficiency (zero holding current) and miniaturization.
• This innovation meets the demanding requirements for next-generation smartphone camera modules.