Method for rapidly implementing sector conversion in multi-beam image sonar

Abstract

The invention provides a method for rapidly implementing sector conversion in a multi-beam image sonar. An acoustic signal is radiated by a transmitting transducer by using the multi-beam image sonar; a target echo is received by a receiving transducer; beam forming processing is performed on the echo data to acquire a target scene image output in a polar coordinate mode; and a sector conversion module is used for conversing the acoustic image of the polar coordinate into the acoustic image of a rectangular coordinate to conform to the visual sense habit. When the sector conversion is realized on the image sonar based on the beam forming, triangular function operation or anti-trigonometric function operation is not needed in the hardware such as field programmable gata array (FPGA). The method comprises the steps of: (1) identifying the resolution ratio of a display used for displaying the acoustic image of a rectangular coordinate; (2) calculating the resolution ratio of horizontal and vertical distances of the image of the rectangular coordinate according to the actual range of the horizontal and vertical distances of the image sonar; (3) calculating the values of the horizontal and vertical coordinates of the polar coordinate corresponding to some point according to the horizontal and vertical coordinates at the point of the image of the rectangular coordinate; (4) obtaining an index value of the horizontal and vertical coordinates of the polar coordinate of the point according to a beam forming principle; (5) storing the image of the polar coordinate image into a memory, reading the corresponding pixel amplitude value according to the index value of the horizontal and vertical coordinates of the polar coordinate, and assigning the value to the position corresponding to the rectangular coordinate; and (6) completing mapping between each point and the polar coordinate under the rectangular coordinate to obtain the acoustic image of the rectangular coordinate.

Description

technical field [0001] The invention belongs to the field of image sonar, and mainly relates to a method for realizing sector transformation in image sonar. Background technique [0002] Multi-beam image sonar often works in an active way, using the transmitting transducer to radiate the acoustic signal, and receiving the target echo through the receiving transducer, the echo data is processed by beamforming to obtain the target scene image, and the image is output in the form of polar coordinates The sector transformation module is used to transform the polar coordinate sound image into a rectangular coordinate sound image, so that it can be displayed on a computer monitor and is suitable for the user's visual habits. [0003] The polar coordinate image output by the beamforming module takes the oblique distance r from the target to the receiving transducer as the abscissa, and the azimuth angle θ of the target relative to the receiving transducer as the ordinate. Sector t...

AI Technical Summary

Problems solved by technology

However, it still needs to consume hardware resources for storage, and some system configurations cannot meet the requirements; another way is to use iterative approximation algorithm (CORDIC algorithm) to calculate trigonometric function values, such as Yang Changgen in his master's degree thesis [Yang Changgen, FPGA-based Acoustic Imaging Algorithm Research and Implementation, Harbin: Master's Degree Thesis of Harbin Engineering University (CNKI), 2006] Using the CORDIC algorithm to realize the sector transformation of the image sonar, but in order to obtain high-precision trigonometric function values, the number of iterations often required is very large

For example, Tan Yiyu et al [Tan Yiyu, Bian Wenbing, A Coordinate Transformation Circuit Based on CORDIC Algorithm, Data Acquisition and Processing, 2001] also used the CORDIC algorithm to realize the fan-shaped transformation of B-ultrasound images, but the calculation accuracy requires High data quantization bits to ensure

Moreover, the implementation of the CORDIC algorithm requires pipeline-based program design, which has certain requirements for developers.

Images