A MEMS-based optical scanning system for precise, high-speed neural interfacing

TL;DR

This paper introduces a MEMS-based optical scanning system with a novel varifocal mirror and custom ASIC, achieving high-speed, high-precision neural interfacing with rapid depth scanning over 12 kHz.

Contribution

The work presents a new MEMS micromirror array and ASIC driver that enable fast, efficient, and precise optical neural interfaces surpassing existing speed and flexibility limitations.

Findings

Achieved over 12 kHz refresh rate for depth scanning

Demonstrated 22 resolvable depth planes

Maintained high diffraction efficiency

Abstract

Optical scanning is a prevalent technique for optical neural interfaces where light delivery with high spatial and temporal precision is desired. However, due to the sequential nature of point-scanning techniques, the settling time of optical modulators is a major bottleneck for throughput and limits random-access targeting capabilities. While fast lateral scanners exist, commercially available varifocal elements are constrained to >3ms settling times, limiting the speed of the overall system to hundreds of Hz. Faster focusing methods exist but cannot combine fast operation and dwelling capability with electrical and optical efficiency. Here, we present a varifocal mirror comprised of an array of piston-motion MEMS micromirrors and a custom driver ASIC, offering fast operation with dwelling capability while maintaining high diffraction efficiency. The ASIC features a reconfigurable nonlinear DAC to simultaneously compensate for the built-in nonlinearity of electrostatic actuators and the global process variations in MEMS mirrors. Experimental results demonstrate a wide continuous sweeping range that spans 22 distinctly resolvable depth planes with refresh rates greater than 12 kHz.