B mode ultrasonic ophthalmological scanners are used widely in clinic diagnosing of eye diseases. Digital Scan Converter (DSC) is a key component in their image processing systems, which performs coordinate transformation and image interpolation between two adjacent scan lines. In this paper, we present a new image processing system scheme based on the FPGA technology. In this scheme, we mainly focus on the DSC component. In the DSC system, we applied the CORDIC algorithm to perform the transformation between Cartesian coordinates and polar coordinates, and use a modified R-theta algorithm to perform the image interpolations. At the same time, we mapped the whole system into a Xilinx FPGA device (XCV50-BG256). Its performance in practical application indicates that the scheme is valid and can improve the image quality significantly and greatly reduce the dimensions of this instrument.