Digital Frame Averaging and Dark Mapping for a Video-Based Underwater Imaging Spectrometer System

A solid-state video camera is used as the focal plane detector in an underwater spectrometer system to acquire multiple spectra simultaneously within the water column. Signal-to-noise enhancement of the spectra is accomplished by use of a combination of frame averaging and dark field mapping so that the dynamic range of the individual frame can be increased from ~7 bits to >13.5 bits. This method also removes the need for shuttering to determine the dark background or device cooling to reduce the dark current noise. The dark mapping algorithm is shown to be valid over a range of device temperatures so that the detector can vary freely with the ambient water temperature without loss in mapping accuracy. Despite observation times that can be up to an order of magnitude greater than cooled devices, the use of frame averaging and dark mapping eliminates the need for additional detector cooldown time and can provide a smaller, simpler, more power efficient, and robust design.