A SURVEY ON VARIOUS IMAGE ENHANCEMENT TECHNIQUES FOR UNDERWATER ACOUSTIC IMAGES

Image enhancement techniques serve as a preprocessing step in segmentation, object detection and recognition in computer vision applications. These techniques may not be suitable for enhancing the acoustic images as the scene of the sea-floor is captured by using special instruments such as Sonar which uses sound as a source to capture image. The acoustic images contain speckle noise which is caused by the interference of the sea-floor sediment and multi-path reverberation. This paper presents a survey on various image enhancement techniques applied on acoustic images. It is recently proved that transformation techniques such as wavelet, curvelet and contourlet are more suitable for removing speckle noises in acoustic images. This paper also provides a framework for understanding the way by which different types of noises in an acoustic image can be removed by filtering techniques.