Application of HDR imaging techniques for sonar images

High Dynamic Range - HDR high resolution recording and processing are required for sonar images when the electronic noise floor from the sensor arrays is well below the ambient acoustic noise floor in the ocean in the frequency bands of interest, while maximum signal levels are determined by the transmitted source level used for the system. Practically one has to handle instantaneous dynamic ranges in excess of 100 dB to support both extremes so that the highlight structure details of close-in bottom features, which are required to classify, are maintained, especially when a number of systems operate in closer proximity. Therefore the data acquisition problems in high frequency high dynamic imaging sonar become critical. Commercially available data acquisition components cannot handle the wide bandwidths and high dynamic range required. An overview of a number of recent techniques based on the use of custom silicon band-pass sigma-delta converters developed for these types of applications is discussed in this paper.