Study on an Ultra-precisely Joining Method for Optical Lenses using a Shrink Fitter

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Optimum Shapes and dimensions of the shrink fitter were obtained using finite element method last year. In the analysis, the physical properties of catalog data for every type of the lens were used. POM was used as the shrink fitter material. In addition, the numerical simulation technique which could consider form error of fitting surfaces of lenses and the housing was developed. It is required that the dimensional accuracy of fitting surface is high, because the shrink fitter method is a shrinkage fit. As a result, the form error of fitting surface is little. Therefore, in the numerical simulation, there was almost no effect of the form error on the contact pressure distribution.The creep tests of polymer materials for shrink fitter, which were started last year, were continued under three kinds of temperature conditions. Four different polymer materials were used. It became that the creep displacement was constant after 500 hours, and further creep displacement was hardly observed.Simpler method of joining the optical lenses was also examined in this fiscal year. The high dimensional accuracy is required in the shrinkage fit. Therefore, the processing cost of the shrink fitter and the housing increases. The processing cost becomes low, if the dimensional tolerance necessary for fitting surfaces can be increased. Then, the periphery of the shrink fitter was turned so that the contact area of fitting surface of the shrink fitter may decrease. As the second method, the housing was cut in one direction, and tightened by the band, after the optical lens and the shrink fitter were inserted in the housing. Those two methods could loosen the dimensional tolerance of the shrink fitter. In addition, it was confirmed that dimensional tolerance of the shrink fitter could be also loosened by positively introducing the form error to the shrink fitter in the numerical simulation.