An Automatic Optical Inspection System for Assembly and Evaluation of an Optical Encoder

Abstract

This study presented an automatic optical inspection system for the assembly and evaluation of an optical encoder, and the system analyzed the output signal quality of the light transmission grating linear encoder. The reference grating was affixed to the side architecture of the detection system in order to maintain the correct optical path, and the main grating was driven by the x–y Precision platform. Brightness variations can be detected and recorded by a charge-coupled device (CCD) camera during grating movements, using image noise depression, background separation, and fringe calculation with new image processing algorithms. The output imaging signal of a traditional linear encoder passes through a circuit filter, where amplification and rectification form a sinusoidal waveform. This system can accurately measure the light intensity variations of the encoder through machine visioning and image processing, while simultaneously determining noise and non-uniformity. This study conducted analysis on the moire width between the gratings of the flip relationship, implemented grating alignment and adjustment, and improved the assembly position and resolution of the image, in order to obtain good quality in output signals.