Resonant Varifocal Micromirror with Piezoresistive Focus Sensor.

Area of Science:

• Optoelectronics
• Microelectromechanical Systems (MEMS)

Background:

• Traditional optical systems often rely on bulky mechanical components for focus adjustment.
• There is a need for compact, integrated solutions for dynamic focal length control.

Purpose of the Study:

• To develop and characterize a microelectromechanical systems (MEMS) resonant varifocal mirror.
• To integrate a piezoresistive focus sensor for real-time focal length monitoring.

Main Methods:

• Fabrication of a varifocal mirror using silicon-on-insulator (SOI) and glass wafers.
• Electrostatic driving of the mirror plate at its resonant frequency.
• Integration of ion-implanted piezoresistors on supporting beams for stress detection.
• Real-time monitoring of focal length via piezoresistor stress variation.

Main Results:

• Achieved a wide scanning range of focal length from -41 mm to 35 mm.
• Operated the varifocal mirror at a resonant frequency of 9.5 kHz.
• Demonstrated real-time monitoring of the varifocal mirror's focal length using the integrated piezoresistive sensor.

Conclusions:

• The integrated MEMS varifocal mirror with piezoresistive sensing offers a compact and efficient solution for dynamic focusing.
• The device shows potential for applications requiring real-time focal length control and wide scanning ranges.