Increased Angle Space for a Fourier Goniometric Flow Cytometer (FGFC) system via Simultaneous Axial and Off-Axis Imaging

Fourier Scatter Imaging (FSI) has proven to be an innovative tool for measuring particle size. This research incorporates Fourier optics into a scatter imaging system with the addition of an off-axis pathway in a Fourier Scatter Microscope. The system uses 0.55 numerical aperture (NA) long working distance objectives that provide angular resolution over +/- 33.4° in the forward direction and 90° +/- 33.4° in the off-axis direction. This setup enables simultaneous capture of axial and off-axis scatter signals using a shared camera, significantly enhancing the angular scattering measurement capabilities. The system is calibrated using a diffraction grating, which provides a well-defined angular reference for analyzing scatter functions. This proof-of-principle system demonstrates the potential for improvements in scattering image resolution. Future iterations will incorporate long working distance objectives with larger NAs (up to 0.90), expanding angular measurements across a range of 218° (from -64° through 154°). The increased angular coverage is expected to enhance the system's ability to measure scatter changes in human cells by incorporating flow cytometry into the system.