Water droplet detection device, and three-dimensional object detection device using water droplet detection device

A three-dimensional object detection device comprising:

• an image capturing unit configured to capture an image of a predetermined area, the image capturing unit having a photographic optical system;
• an image conversion unit programmed to perform viewpoint conversion of the image obtained by the image capturing unit to a bird's-eye-view image;
• a water droplet detection unit programmed to set an arbitrary attention point in the image obtained by the image capturing unit, a plurality of first reference points inside an imaginary circle of a predetermined radius having the attention point as a center the imaginary circle, and a plurality of second reference points corresponding to the first reference points outside the imaginary circle, the water droplet detection unit being further programmed to detect edge information between the first reference points and second reference points, and the water droplet detection unit being further programmed to assess a circularity strength of the edge information, thereby detecting a water droplet attached to the photographic optical system;
• a three-dimensional object detection unit programmed to detect a presence of the three-dimensional object based on the pixel distribution data by detecting information on pixel distribution in the bird's-eye-view image obtained by the image conversion unit, for which the luminance difference is equal to or greater than a predetermined first threshold value in a direction in which a three-dimensional object collapses upon viewpoint conversion to the bird's-eye-view image, and, detects the three-dimensional object when a degree of distribution of the pixels is equal to or greater than a predetermined second threshold value in the direction in which the three-dimensional object collapses;
• a three-dimensional object assessment unit programmed to access whether or not a three-dimensional object in a detection area that has been detected by the three-dimensional object detection unit is another vehicle;
• and
• a controller programmed to control the vehicle in accordance with a state of attachment of water droplets in a detection area detected by the water droplet detection unit.

A water droplet detection method for detecting water droplets attached to a photographic optical system of an image capturing unit comprising a photographic optical system, the water droplet detection method comprising:

• setting an arbitrary attention point in the captured image that has been acquired by the image capturing unit, a plurality of first reference points inside an imaginary circle of a predetermined radius having the attention point as a center the imaginary circle, and a plurality of second reference points corresponding to the first reference points outside the imaginary circle, each of the second reference points being set on a straight line connecting the attention point and the corresponding one of the first reference points;
• detecting edge information between the first reference points and the second reference points;
• determining a circularity strength of the edge information as a ratio of a number of pairs of the corresponding first and second reference points between which the edge information was detected to a total number of the corresponding first and second reference points;
• assessing that a water droplet is attached to the photographic optical system at a location corresponding to the imaginary circle when the circularity strength is equal to or greater than a prescribed ratio.