A multi-mode digital holographic microscope

Journal article

We present a transmission-mode digital holographic microscope that can switch easily between three different imaging modes: inline, dark field off-axis, and bright field off-axis. Our instrument can be used: to track through time in three dimensions microscopic dielectric objects, such as motile micro-organisms; localize brightly scattering nanoparticles, which cannot be seen under conventional bright field illumination; and recover topographic information and measure the refractive index and dry mass of samples via quantitative phase recovery. Holograms are captured on a digital camera capable of high-speed video recording of up to 2000 frames per second. The inline mode of operation can be easily configurable to a large range of magnifications. We demonstrate the efficacy of the inline mode in tracking motile bacteria in three dimensions in a 160 μm × 160 μm × 100 μm volume at 45× magnification. Through the use of a novel physical mask in a conjugate Fourier plane in the imaging path, we use our microscope for high magnification, dark field off-axis holography, demonstrated by localizing 100 nm gold nanoparticles at 225× magnification up to at least 16 μm from the imaging plane. Finally, the bright field off-axis mode facilitates quantitative phase microscopy, which we employ to measure the refractive index of a standard resolution test target and to measure the dry mass of human erythrocytes.

Authors: Flewellen, J; Zaid, I; Berry, R

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: AIP Publishing
• Journal: Review of Scientific Instruments
• Volume: 90
• Issue: 2
• Pages: 023705
• Publication date: 2019-02-25
• Acceptance date: 2019-01-31
• DOI: 10.1063/1.5066556
• EISSN: 1089-7623
• ISSN: 0034-6748