Optics and Actuation Co-Design for an Implantable Reflectance Confocal Microscope with Large Working Distance

We discuss optical and actuator design considerations in developing a miniature reflection confocal microscope (RCM) based on parametrically-resonant MEMS micro-mirrors. Microscope form factor targets real-time imaging of the brain in small animals, at subcellular resolution. Candidate designs start with a combination of lens sequence, micro-mirror size, and scanning angle, within packaging dimensions for eventual implantation on a freely-behaving mouse. Design optimization focuses on maintaining the diffraction-limited resolution over large field-of-view (FOV), while ensuring large feasible micro-mirror operating frequency. After investigation of optical configurations and required mirror performance over tradeoffs such as working distance (WD) and numerical aperture (NA), we demonstrate a system providing 1.5µm lateral and 6µm axial resolution with 350×350µm FOV and 303 µm WD.