Patent US 5,287,293

A method and apparatus for the automatically inspecting the contours of a gear for manufacturing errors. According to the method, a gear to be inspected is imaged on an imaging surface to form a gear image. A digitized image indicative of the gear image is generated. The digitized image comprises a plurality of pixels. The pixels each have a gray value and coordinates which represent the location of the pixel within the digitized image. Each pixel is classified into a first or a second class by comparing the gray value of the pixel to a predetermined threshold value. The coordinates of pixels corresponding to the contours of the gear are determined from the classes of pixels. The manufacturing errors of the gear are calculated by comparing the coordinates of the pixels corresponding to the contours of the gear to a standard gear pattern. The apparatus, in its preferred embodiment, includes a base and collimated light source to illuminate the gear, a microscope to magnify an image of the gear and a CCD camera to generate a digitized image indicative of the magnified gear image. A digital computer is also included to assign a gray value to each pixel in the digitized image, to classify each pixel into a first or second class by comparing the gray value of the pixel with a predetermined threshold value, to determine the coordinates of pixels corresponding to the contours of the gear and to calculate the manufacturing errors of the gear by comparing the coordinates of pixels corresponding to the contours of the gear with a standard gear pattern. The manufacturing errors include runout error, pitch error and profile error.