A micromirror array with annular partitioning for high-speed random-access axial focusing.

Area of Science:

• Optics and Photonics
• Micro-optics
• Adaptive Optics

Background:

• Dynamic axial focusing is crucial for microscopy, AR/VR, and material processing.
• Existing varifocal technologies face trade-offs between speed, dwelling capacity, and operating overhead.
• Low-refresh-rate devices (e.g., liquid crystal lenses) and high-speed devices sacrificing capabilities (e.g., deformable mirrors) limit system performance.

Purpose of the Study:

• To present a general-purpose random-access axial focusing device overcoming limitations of current varifocal tools.
• To enable high speed, dwelling capacity, and lightweight drive simultaneously.
• To offer a solution for bottlenecked applications in optics and imaging.

Main Methods:

• Development of a micromirror array (8.2 mm diameter) with 48-μm-pitch piston-motion pixels.
• Utilizing low-rigidity micromirrors and defocusing phase profiles for axial focusing.
• Electrically partitioning pixels into 32 rings for phase-wrapped operation with circular symmetry, requiring <30 V per channel.

Main Results:

• Achieved 2π phase shifting for wavelengths < 1100 nm.
• Demonstrated a 10-90% settling time of 64.8 μs, enabling a 15.44 kHz refresh rate.
• Optical experiments confirmed a wide focusing range, targeting 29 distinct resolvable depth planes.

Conclusions:

• The proposed micromirror array successfully bridges the gap between high speed and dwelling capacity in axial focusing.
• The device offers compact and straightforward implementation for demanding optical applications.
• Potential applications include high-throughput single-cell targeting in neurobiology and dense 3D visual information delivery in AR/VR.