Point cloud mean background subtraction based method for 3D sonar image modeling

Patent metadata

Field	Value
Publication number	US-11217018-B2
Application number	US-201716075946-A
Country	US
Kind code	B2
Filing date	Dec 8, 2017
Priority date	Mar 8, 2017
Publication date	Jan 4, 2022
Grant date	Jan 4, 2022

Abstract

The present invention discloses a point cloud mean background subtraction based method for 3D sonar image modeling, comprising: (1) obtaining sonar data, and convert 3D sonar range image information corresponding to sonar data per frame into point cloud data for overall coordinate; such point cloud data will form image pixels; (2) taking the mean value u(x,y,z) of pixels at the same position in a series sequential frame images as pixels at the same position in the background model to obtain the background model; define threshold value TH for background standard based on pixel in each image; (3) testing current frame image I(x,y,z) based on background model and threshold value TH to obtain output image; (4) using current frame image I(x,y,z) to update background model and threshold value TH. Such method can quickly identify prospect target in the background, and establish corresponding arithmetic model for further processing; it features in quick processing, which can automatically update background model according to changing environment.

First claim

The invention claimed is:

1. A point cloud mean background subtraction based method for three-dimensional (3D) sonar image modeling, comprising the following steps:
(1) obtaining sonar data including corresponding 3D sonar range imagine information, and converting the 3D sonar range image information corresponding to the sonar data per frame into point cloud data for overall coordinate (x, y, z), such point cloud data forming 3D image pixels, wherein pixel value of the 3D image pixels comprises positional value defined by the overall coordinate (x, y, z) and corresponding sonar signal intensity value at such position;
(2) calculating and using mean value u(x,y,z) of 3D image pixels at same position in a series of sequential frame images as pixels at the same position to obtain a background model; determining threshold value TH for background standard based on pixel in each frame of image;
(3) testing current frame of image I(x,y,z) based on the background model and the threshold value TH to obtain an output image;
(4) using the current frame of image I(x,y,z) to update the background model and the threshold value TH;
wherein u(x,y,z) refers to the mean sonar signal intensity at coordinate (x, y, z), I(x,y,z) refers to the current frame of image at coordinate (x, y, z), TH refers to a threshold value based on mean value of all pixel differences and standard deviation to all pixel differences.

2. The point cloud background subtraction based method for 3D sonar image modeling according to claim 1 , wherein specific procedures of the Step (2) are as follows:
(2-1) uniformly marking positions without point cloud data in a series of sequential frame images as void to obtain a pretreated image set;
(2-2) calculating mean value u(x,y,z) of pixels at the same position of all images in a pretreated image set, and taking the mean value as pixels at the same position to obtain the background model;
(2-3) calculating absolute value F (t) (x,y,z) of pixel difference at the same position of two adjacent frame of images and mean value u diff (x,y,z) of all absolute values of pixel difference; the formula used being as follows:

F

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wherein, I t (x,y,z) refers to pixel value at coordinate (x, y, z) of image at the time t; gap refers to time interval between two frame images; I t-gap (x,y,z) refers to pixel value at coordinate (x, y, z) of image at time t-gap; M refers to total frames of images;
(2-4) calculating standard deviation to all pixel differences diff std (x,y,z); the formula used is as follows:

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Assignees

• Univ Zhejiang

Inventors

• Liu Xuesong
• Zhou Fan
• Chen Yaowu

Classifications

• G06T7/254 Primary

  involving subtraction of images · CPC title

• G06T2207/10028

  Range image; Depth image; 3D point clouds · CPC title

• G06T2207/10136

  3D ultrasound image · CPC title

• G06T7/136

  involving thresholding · CPC title

• G06T19/00 Primary

  Manipulating three-dimensional [3D] models or images for computer graphics · CPC title