3D-scanning and miniature MPM objective with improved resolution at depth scanning

Achieving 3D imaging in a compact handheld or microendoscopic MPM system requires a miniature objective and scanner. We report on a miniature objective design that can perform depth scanning and maintain good focusing performance over a wide depth scanning range. Our objective was composed of an aspheric lens and a plano-convex lens (PCX). Depth scanning was achieved by actuating the aspheric lens using a shape memory alloy actuator. The challenge of focal spot degradation during depth scanning was addressed by compensating the spherical aberration induced by refractive index mismatch with that by the curvature of the PCX. Compared with other aspheric lens-based objectives and gradient index objective, our custom objective improved the performance in focal spot degradation and penetration depth. The resolution and signal intensity remained fairly constant over ∼400 µm depth scanning range. The advantages of depth scanning and deep penetration in a miniature profile of our objective design show great potential in clinical MPM applications.