Intelligent sensor method and apparatus for an optical wheel alignment

Abstract

A sensor method and apparatus for an optical wheel alignment machine utilizes one or more light sources, such as lasers, to project a laser line or other shaped light onto various locations about the sidewall of a tire undergoing measurement. The sensor includes a video camera or other light responsive receiver and a optical system that combines the reflected laser lines into a single image that is received by the camera. The optical system also rotates one or more of the reflected laser lines so that all of the reflected portions have the same general orientation upon entering the camera. The camera outputs a video data stream that is indicative of the image. The sensor has an electronic circuit that analyzes this video data stream in real time to determine the location in the image of a preselected feature of each of the laser lines. The circuit then outputs coordinate data indicative of the location of this feature. The circuit is microprocessor-based and uses a comparator that compares the incoming video data stream with a threshold to determine, on a pixel-by-pixel basis, whether any particular pixel lies on or outside one of the laser lines received by the camera. For a pixel lying on a laser line, the comparator interrupts operation of the microprocessor which then determines the position within the image of that pixel. Once the pixel representing the preselected feature is found, the microprocessor uses that information to generate the coordinate output data.