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

Patent metadata

Field	Value
Publication number	US-2021217240-A1
Application number	US-201716075946-A
Country	US
Kind code	A1
Filing date	Dec 8, 2017
Priority date	Mar 8, 2017
Publication date	Jul 15, 2021
Grant date	—

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

1 . A point cloud mean background subtraction based method for 3D sonar image modeling, comprising the following steps:
(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 forming 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; defining 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.

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

u
diff

⁡

(

x
,
y
,
z

)

=

1
M

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∑

t
=

gap
+
1

M

⁢

F
t

⁡

(

x
,
y
,
z

)

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

diff
std

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(

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,
y
,
z

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=

1
M

⁢

∑

t
=

gap
+
1

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(

F
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-

u
diff

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2

(2-5) defining threshold value TH based on mean value u diff (x, y, z) of all pixel differences and standard deviationdiff std (x, y, z) to all pixel differences; the formula used is as follows:
TH= u diff ( x,y,z )+β×diff std ( x,y,z )

wherein, β is threshold factor.

3 . The point cloud mean background subtraction based method for 3D sonar image modeling according to claim 1 , characterized in that specific procedures of the Step (3) are stated as follows: subtracting pixel u(x, y, z) at the same position of background model from pixel I(x, y, z) of current frame image to obtain pixel difference d(x,y,z); comparing such pixel difference d(x, y, z) with threshold value TH to obtain output image output(x,y, z) as follows:

output
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,

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d
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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

• G06T7/136

  involving thresholding · CPC title

• G06T7/194

  involving foreground-background segmentation · CPC title

• G06T2207/10136

  3D ultrasound image · CPC title