Integrating Optics and Parametrically-Resonant Micro-Scanner Design for Large Working Distance Implantable Microscopy

This article examines interdependent design of an optical path and a microelectromechanical system (MEMS) scanning mirror for a miniature, implantable fluorescence microscope with large working distance (WD). Linearized and numerical ray analyses are used to approximately decouple optical and mechanical functions during design. We then maximize scan rate in the scenario of high-NA focusing with a specified WD and field-of-view (FOV). To do so, dynamic rotational analysis is combined with a novel model for expected failure voltage of parametrically-resonant electrostatic MEMS scanning mirrors. Mirrors parameters are set to optimize mirror speed within constraints fixed by optical specifications, while compatible optical path is selected for small objective diameter. A prototype instrument achieving sub-cellular resolution up to approximately <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>500</mml:mn> <mml:mspace></mml:mspace> <mml:mi>x</mml:mi> <mml:mspace></mml:mspace> <mml:mn>500</mml:mn> <mml:mspace></mml:mspace> <mml:mi>μ</mml:mi> <mml:msup><mml:mrow><mml:mi>m</mml:mi></mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:msup> </mml:math> FOV at up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mn>300</mml:mn> <mml:mspace></mml:mspace> <mml:mi>μ</mml:mi> <mml:mi>m</mml:mi></mml:math> WD is validated on imaging targets and excised mouse brain tissue.