Ultra-Precision Method of Joining Optical Lenses Using a Shrink Fitter

Abstract

An ultra-precision method of joining optical lenses in the cell has been developed by using a shrink fitter, in order to produce a laser scanner having a wide field of vision and high resolution. In a current method, optical axes of the lenses in the cell do not coincide with each other, when environmental temperature changes, because of great difference in thermal expansion coefficients between the lenses and the cell. Therefore, the laser spot cannot be converged to a designed size on an image plane. A shrink fitter, which has a higher thermal expansion coefficient than the lenses and the cell do, was inserted between them. The positioning accuracy of the lenses in the cell did not change at any temperature since the shrink fitter sufficiently expanded or contracted in the radial direction to compensate the change in interference. As a result, the lens unit assembled by the new method worked out to converge the laser beam over a wide scanning width. In this paper, we examined the shrink fitter theoretically and experimentally.