Light from an object such as a cell moving through an imaging system is collected and dispersed so that it can be imaged onto a time delay and integration (TDI) detector. The light can be emitted from a luminous object or can be light from a light source that has been scattered by the object or can be a fluorescent emission by one or more FISH probes, frequently used to detect substances within cells. Further, light that is absorbed or reflected by the object can also be used to produce images for determining specific characteristics of the object. The movement of the object matches the rate at which a signal is read from the TDI detector. Multiple objects passing through the imaging system can be imaged, producing both scatter images and spectrally dispersed images at different locations on one or more TDI detectors.