Indian Journal of Science and Technology

Abstract

Background/Motivation: Optical image captured by autonomous underwater vehicles need to be preprocessed as they suffer from various adversary underwater conditions and require low power devices such as FPGA. Methods/ Statistical Analysis: Underwater image degradation due to non uniform illumination is corrected by non linear filtering and is implemented in FPGA. Two dimensional Fast Fourier Transform (FFT) and its inverse along with logarithmic computation were implemented in FPGA as a part of filter implementation. One dimensional row wise and column wise FFT were computed first and then combined to form two dimensional FFT. Findings: FPGA’s can be used for implementing architectures that require high level parallelism such as image processing algorithms due to its inherent parallelism. Frequency based filtering method which is employed for preprocessing an underwater image successfully provided good histogram compared to the original one. Device utilization for implementing structure was estimated. Novel method of FFT implementation, its inverse and logarithmic computation was used in this work. The method can be applied to digital signal processing applications that can be implemented in FPGA. Application/Improvements: Automation of image preprocessing is required in unmanned underwater vehicles used for cable detection, navigation etc. These vehicles are to be provided with low power devices such as FPGAs for long run in underwater applications.
Keywords: Automated Underwater Vehicles, FPGA, Fast Fourier Transform, Nonlinear Filtering, Underwater Image Enhancement