Raindrop are detected to glass pane by means of video camera and illumination

摘要

The invention relates to a method for detecting rain drops (4) on the outer side (2.2) of a window pane (2) by means of a camera (1) arranged behind the window pane (2) and focused on a long-distance range in front of the window pane, and an illumination source (3) for generating at least one light beam (h) directed onto the window pane (2) in such a way that at least one beam (r2; r2') reflected from the outer side (2.2) of the window pane (2) impinges on the camera (1), wherein the method comprises the following steps: capturing a sequence of images (5.1, 5.2, 5.1', 5.2') using the camera (1) for a driver assistance function, wherein the capturing of the image sequence is divided into temporally constant function cycles (6, 6'), a first and second capture (5.1, 5.2, 5.1', 5.2') of a respective image occurs temporally consecutively in each function cycle (6, 6') and the time interval (dt, dt') between the first and second capture (5.1, 5.2, 5.1', 5.2') is varied from function cycle (6) to function cycle (6'); generating the light beam (h; 5.4, 5.4') directed onto the window pane (2) using the illumination source (3) in a function cycle within the time interval between the first and second capture (5.1, 5.2, 5.1', 5.2'), wherein a third capture of an image (5.3, 5.3') is made in this function cycle for a rain detection function such that the at least one beam (r2; r2') reflected from the outer side (2.2) of the window pane (2) can be at least partially recorded by the camera (1); and evaluating the amount of light of the at least one, at least partially recorded beam (r2; r2') reflected from the outer side (2.2) of the window pane (2) in order to detect rain (4) on the outer side (2.2) of the window pane (2).