Research Of Light Image Distortion Based On Headlamp Tester

Headlamp is an essential device when motor vehicle is driving at night, and it is installed correctly or not relates to the driver's lives and property. For this reason, there are clear provisions in the national standard for motor vehicle headlamps. At the same time, in order to ensure traffic safety, we must carry out regular inspection of motor vehicle headlamps. It is very important to ensure detection's precision for accurately reflecting situation of headlight installation.The article analyzed detection index that prescribed in the national standard of headlight tester, and known headlight tester should measure which index about headlight beam. Simultaneously, the article analyzed test principle and test process what existing headlight tester has contained. Most of existing automatic headlight tester introduced image sensor to capture images of the headlight beam, and then used digital image processing techniques to process spot image. Ultimately, we got relational parameters that headlight beam hold. But none of the existing majority of the tester has corrected image distortion that caused by installing angle of image sensor, which reducing detection accuracy of tester.Therefore, the article analyzed reasons of image distortion and effect caused by distortion to detection accuracy, and proposed a algorithm of distortion correction. To verify the effectiveness of the algorithm, the article did a corrected experiment on distorted concentric rings.Firstly, the article used pure software approach to correct distorted concentric rings in the C++ platform, and experimental results show effectiveness of the proposed algorithm. However, most of existing automatic headlight tester used DSP to process digital image, in order to validate effection of the algorithm that the article has proposed in DSP digital processing platform, the algorithm is transplanted to the DSP platform-TDS642EVM and programmed to correct distortion in the software development platform-CCS. After comparing the images, the results proved that the proposed algorithm is also effective on the DSP platform.The image distortion correction that the article has done is the improvement on existing headlight tester, and improved accuracy of detection through correcting to distorted image, and also provided some help to safety of driving at night, thus reducing people's loss of life and property.