Research On Digital Scan Conversation In B Mode Ultrasonic System

Digital scan conversion is an important part of B mode ultrasonic. Traditional digital scan conversion accomplishes the joint of ultrasonic scan and displaying scan, provide a temporary memory for image, make the real time disposal of ultrasonic image be possible. The digital scan conversion in the thesis includes signal pretreatment, digital image process, keeping signal temporarily and transforming coordinate. It is a broad conception. This thesis discusses the digital filter and the transforming coordinate in digital scan conversion particularly, not only completing them in theory, but also accomplishes them by FPGA.In the part of accomplishing dynamic filter, This thesis analyzes and validates the relation between the attenuation of ultrasonic via human structure and the ultrasonic frequency. To get the best resolving power of the echo diagram in the whole depth, this thesis builds the FIR dynamic filter by EP1C6Q240 of Cyclone of Altera corporation, shows the hardware diagram of filter and the process of calculating parameters. At last, this thesis compares and analyzes the diagrams which are created by B mode ultrasonic using dynamic filter and B mode ultrasonic using const filter.In the part of transforming coordinate, the thesis gets the conclusion of the essential of transforming right angle coordinates to polar coordinates by introducing the concepts of ultrasonic scan and displaying scan. Introducing the process and the arithmetic of transforming right angle coordinates to polar coordinates. This thesis indicates the advantage of describing formulary. By comparing to the common arithmetic, this thesis educes the CORDIC which is more suitable to be accomplished by hardware. At last this thesis discusses the difficulties of transforming coordinate by describing formulary, educes the method of enhancing the real time.