The Study On Displacement Measurement With Digital Image Processing

The three-coordinates measure machine is the main and all-purpose instrument, it is mainly used to measure the size of form and position of the workpiece ,such as workpiece outline .Because of complicated structure large system and high price, the instrument is limited in range of application. In order to measure the outline of workpiece, which isn't high precision, it is demanded that a new three-coordinates measure machine with middle or low precision and good function and low price would be researched and developed.The article involves the part of the problem, it is described that how to measure straight line-displacement in the three-coordinates measure of form and position. The straight line-displacement measure is the base measuring method, which includes X Y direction measure, according to the accumulation and synthesis of straight line-displacement along the two direction, shape workpiece can be measured. It is the problem in the article that how to realize the measure of straight line-displacement in low accuracy. It is described in the article that in low accuracy the measure of straight line-displacement can be got with the picture processing. In the method the movie camera fixed on the sliding foundation can set the continuous pictures of granite reference platform, hen the continuous pictures are treated with picture processing, comparing the each property sphere inside close picture and making use of the irrelevant moment shape, the characteristic quantity of Fourier descriptor can be corrected, by means of matching through in every stage of its passage and find the same property sphere then according to the second picture element positioning the opposite displacement can be found in the property sphere inside close picture. Because the light of system shines and the distance between the movie camera and granite reference are invariable, the displacement represented by every picture element can be got beforehand by the means of experiment mark method. Thus in the actual measure, with solving the opposite displacement represented by the picture element in property sphere, the actual displacement represented in the close picture can be got. With accumulating and synthesizing, the displacement of movie camera represented by whole image sequence, and then the coordinates value of sliding foundation straight line-displacement, the low cost regeneration of the three-coordinates measure machine in low accuracy would came true.