Large aperture tunable-focus liquid lens using shape memory alloy spring.

Area of Science:

• Optics and Photonics
• Materials Science
• Mechanical Engineering

Background:

• Traditional lenses have fixed focal lengths, limiting adaptability in optical systems.
• Tunable lenses are crucial for applications requiring variable focus, such as adaptive optics and compact imaging devices.
• Existing tunable lens technologies often face challenges with aperture size, power range, or actuation complexity.

Purpose of the Study:

• To develop and demonstrate a large-aperture liquid lens with a tunable focus capability.
• To utilize shape memory alloy (SMA) springs as efficient actuators for precise optical power adjustment.
• To characterize the optical performance, including power range and wavefront error, of the fabricated tunable lens.

Main Methods:

• Constructed a liquid lens comprising a liquid-filled cavity, a compressible annular rim, a flexible membrane, and a rigid base.
• Employed three SMA springs to actuate the annular rim, controlling the membrane's curvature and thus the lens's focal length.
• Utilized a Shack-Hartmann wavefront sensor to measure the optical performance and wavefront error across the tunable power range.

Main Results:

• Achieved a tunable optical power range from 0 to 4 diopters with a driving voltage below 3V.
• The fabricated lens has a large aperture diameter of 34 mm and a thickness of 9 mm, weighing 16.7 g.
• Demonstrated RMS wavefront errors of 0.77 µm at 0 D and 1.68 µm at +4 D, indicating good optical quality.

Conclusions:

• The SMA-actuated liquid lens offers a viable solution for large-aperture, tunable-focus optical systems.
• The low-voltage operation and broad diopter range highlight its potential for various imaging and optical applications.
• This design advances tunable lens technology, providing a compact and efficient alternative to conventional optics.