US 9,811,746 B2
Method and system for detecting traffic lights
Yankun Zhang, Shanghai (CN); Chuyang Hong, Shanghai (CN); Ruyi Jiang, Shanghai (CN); Yun Zhou, Shanghai (CN); and Norman Weyrich, Shanghai (CN)
Assigned to Harman International Industries, Incorporated, Stamford, CT (US)
Appl. No. 14/646,337
Filed by Harman International Industries, Incorporated, Stamford, CT (US)
PCT Filed Nov. 20, 2012, PCT No. PCT/CN2012/084862
§ 371(c)(1), (2) Date May 20, 2015,
PCT Pub. No. WO2014/078979, PCT Pub. Date May 30, 2014.
Prior Publication US 2015/0294167 A1, Oct. 15, 2015
Int. Cl. G06K 9/00 (2006.01); G06T 1/00 (2006.01); G06K 9/46 (2006.01)
CPC G06K 9/00825 (2013.01) [G06K 9/4652 (2013.01); G06T 1/0007 (2013.01); G06T 2207/10004 (2013.01); G06T 2207/10024 (2013.01); G06T 2207/30252 (2013.01)] 21 Claims
OG exemplary drawing
 
1. A method for detecting traffic lights, comprising:
obtaining a color image captured by a camera;
converting the color image into a first monochrome scale image
converting the first monochrome scale image into a first binary image wherein the color image is converted into the first monochrome scale image based on a first threshold of brightness;
identifying a first set of candidate blobs in the first binary image based on at least three predetermined geometric parameters, wherein the at least three predetermined geometric parameters comprise a range of pixel number, a width range, and a range of width to height ratio;
determining whether a first region in the color image, which corresponds to one of the first set of candidate blobs, represents a green traffic light using a green traffic light classifier;
converting the color image into a second binary image, wherein the color image is converted into the second binary image based on a second threshold, the second threshold being determined based on camera parameters including at least one of a color gamut and a color saturation;
identifying a second set of candidate blobs in the second binary image; and
determining whether a second region in the color image, which corresponds to one of the second set of candidate blobs, represents a red traffic light using a red traffic light classifier.