1. A method of scanning of fluorescent light emitted from fluid samples: placing fluid samples in at least one sample holder in a rotating carousel that is simultaneously moved in a linear direction, the fluid samples having fluorescent light emitting target substances; scanning over a non-surface plane of the fluid samples with R-theta scans of a beam spot and detecting levels of emitted fluorescent light from the scanned plane at locations that define emitted fluorescent light volumes of interest, as well as bulk fluorescence emission; and mapping volumes of interest in the scanned plane, as well as deriving therefrom the bulk fluorescence emission.