The realization of strain measurement based on digital image processing technique is discussed. Combined with the strain measurement principle and the optical imaging feature, considered the axisymmetrical and non-axisymmetrical distortion, the automatic surface-fitting calibration method based on region growing is adopted. Cubic polynomial is applied to establish the relationship between the object space and pixel coordinate system. The expectations based on wavelet coefficients are used for sub-pixel edge detection, measurement accuracy can reach 0.02 pixels. Accuracy of displacement for strain measurement achieves micrometer-level. The theoretic validity and practical feasibility of the system are proved by the strain measurement of a cantilever steel beam.

The profile error of the gear surface of worm produces a great impact to gear characteristic. So, it is necessary to calculate the profile error of the gear surface. In order to develop the manufacturing accuracy of the complex tooth surface of the worm pair, a method to measure the error of the worm was designed in this paper. The profile error of the worm can be calculated based on geometrical operation. To meet the need of quality-controlling and the intelligent machining, the 3-D measuring technology method was adopted to measure the surface of the worm. And through the calculation, analysis and reconstruction, the real outline of the worm pair is redrew. A whole theoretical solid model of worm’s meshing surface with grid can be obtained based on the mathematical modeling. And it is possible to give the data of the recorrection and the feedback by analysing the profile error.