Research Of Self-calibration For Small Modulus Gears Visual Measuring System

Small modulus gear is an important component in precision instrumentsindustry. Measuring the geometric is of great significance. The contact measurementis the most conventional method. This method is disabled to smaller gears, as theprobe’s crafts limited. This paper applies machine-vision measurement technology inthe small modulus gear field. The gear measuring hardware platform has been built.All the contents are based on this platform. There are two parts to be researcheddeeply. One is about the image de-noise, the other is about the self-calibration.The main content of this article contains the following4aspects:Firstly, the pictures being used for calibration are accompany with a largemount of noise. In order to get a better edge of the gear, the de-noise method shouldbe researched. In the Curvelet transform region, as the gear has symmetry, thecorrelation can be fully used in this method. A new algorithm combine the scale anddirection de-noise is proposed.Secondly, On the traditional camera calibration’s aspect, by making use of theGerman Marh’s precision calibration block realizes the system’s traditional cameracalibration research. By the end of this part, the scale factor of the imaging system is1.1μm/pixel.Thirdly, On the camera self-calibration’s aspect, comparing the distancemeasured by the grating and the image distance of4feature points on differentpictures, the scale factor of the imaging system is1.1μm/pixel. It matched thetraditional’s data. It proves the self-calibration’s feasibility.At last, put the model into practice. Get the gear’s edge in world coordinates.Then put it in gear’s evaluation system to calculate parameters. By comparing theNational Jiliang Center’s result, the pitch deviation between two methods is±5μm.