title: Modulated-alignment dual-axis (MAD) confocal microscopy for deep optical sectioning in tissues.
abstract: A strategy is presented to enable optical-sectioning microscopy with improved contrast and imaging depth using low-power (0.5 - 1 mW) diode laser illumination. This technology combines the inherent strengths of focal-modulation microscopy and dual-axis confocal (DAC) microscopy for rejecting out-of-focus and multiply scattered background light in tissues. The DAC architecture is unique in that it utilizes an intersecting pair of illumination and collection beams to improve the spatial-filtering and optical-sectioning performance of confocal microscopy while focal modulation selectively 'labels' in-focus signals via amplitude modulation. Simulations indicate that modulating the spatial alignment of dual-axis beams at a frequency f generates signals from the focal volume of the microscope that are modulated at 2f with minimal modulation of background signals, thus providing nearly an order-of-magnitude improvement in optical-sectioning contrast compared to DAC microscopy alone. Experiments show that 2f lock-in detection enhances contrast and imaging depth within scattering phantoms and fresh tissues.
authors.affiliation: Stony Brook University (SUNY), Department of Biomedical Engineering, Stony Brook, NY 11794, USA.
authors.forename: Steven Y
authors.initials: SY
authors.lastname: Leigh
authors.affiliation: Stony Brook University (SUNY), Department of Biomedical Engineering, Stony Brook, NY 11794, USA.
authors.forename: Ye
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Stony Brook University (SUNY), Department of Biomedical Engineering, Stony Brook, NY 11794, USA.
authors.forename: Jonathan T C
authors.initials: JT
authors.lastname: Liu
keywords: (110.0113) Imaging through turbid media; (170.1790) Confocal microscopy; (170.2520) Fluorescence microscopy; (170.4090) Modulation techniques; (170.5810) Scanning microscopy; (230.1040) Acousto-optical devices