METHOD FOR DETERMINING A STATE OF OBSTRUCTION OF AT LEAST ONE CAMERA INSTALLED IN A STEREOSCOPIC SYSTEM

摘要

To improve the performance for determining obstruction of a stereoscopic system using two cameras or more, a hybrid of local and semi-global methods is provided. For each stereoscopic image formed from simultaneous left and right images, a breakdown of each left and right image into corresponding sectors is applied. Obstruction level is determined by a disparity map by sector, based on left or right images, and in which a disparity is assigned to each pixel corresponding to the best matching score. A determination of density by sector of the disparity map is carried out by reference to a fraction of pixels with a disparity considered to be valid. A state of obstruction of at least one camera is determined based on a weighted average of the probabilities of obscuring of the sectors of the disparity map obtained by comparison between the density of the sectors and a predefined density level.

主权项

1. A method for determining a state of obstruction of at least one camera in a multi-camera system installed on board a vehicle comprising the following steps:
acquisition of the successive stereoscopic images of a field of view, each stereoscopic image from the multi-camera system being formed from left and right images (11, 12) produced simultaneously and digitally stored in the form of pixels, calculation of a disparity map based on successive multi-camera images, and calculation of a level of obstruction as being a weighted average determined by the following steps: breakdown of the disparity map (20) into sectors (10), determination of the density of each sector (10) by the fraction of pixels with a disparity considered to be valid (108), determination of a probability of stereo obstruction by sector (109) of the disparity map (20) by comparison between the density of this sector (10) and a predefined level of obstruction, and determination (119) of a weighted average of the probabilities of obscuring of the sectors (10) as a function of a weighting (118) of the position of these sectors (10) within the disparity map (20),wherein the method furthermore comprises a complementary mono-stereo combined analysis test including the following steps in order to determine the presence of an object in front of a camera:
selection (112) of one of the two stereo images (11; 12) to be analyzed, referred to as mono image; breakdown (113) of this mono image (11; 12) into sectors (10a) with the same dimensions as those (10b) of the disparity map (22) in order to form a mono map (32); calculation (114) of a probability of mono obstruction by sector (10a) of the mono image (11; 12), carried out by an edge detection analysis and a detection of characteristic points using the detection data, transferred onto the mono map (32); comparison of the probabilities of stereo and mono obstruction, then merging (115) between the disparity map (22), having the probabilities of stereo obstruction (109) by sector (10b) and the mono map (32), having the probabilities of mono obstruction (114) by sector (10a), by assigning to each sector (10b) of the disparity map (22) the lowest probability of obstruction, corresponding to the highest density, so as to generate a disparity map referred to as merged (42); and if the probability of merged obstruction is globally less than the probability of stereo obstruction (test 116), the camera corresponding to the image being analyzed (11; 12) is considered as potentially obstructed and a processing is triggered (117);in the opposite case, an object is considered as having masked the field of view of the camera being analyzed.