Methods and systems are provided to facilitate simultaneous high-resolution microscopic imaging of cells and detection of side-scattered light from such cells using an immersion objective. A container maintains a volume of an immersion oil or other immersion fluid in contact with the immersion objective and with a stage that contains a sample of the cells. The container also includes a window through which the cells can be illuminated off-axis to generate side-scattered light. The side-scattered light can then be detected through the immersion objective. The container maintains the immersion fluid in contact with an internal surface of the window to control the geometry of the optical interface between the off-axis illumination source and the immersion fluid. These systems permit high-throughput identification and imaging of cells for biological research, improvement of side-scatter cell classifiers, improved high-throughput cell sorting, and other applications.